UI: Redesigned data-block selectors

The previous design is rather old and has a couple of problems:

* Scalability: The current solution of adding little icon buttons next to the
  data-block name field doesn't scale well. It only works if there's a small
  number of operations. We need to be able to place more items there for better
  data-block management. Especially with the introduction of library overrides.
* Discoverability: It's not obvious what some of the icons do. They appear and
  disappear, but it's not obvious why some are available at times and others
  not.
* Unclear Status: Currently their library status (linked, indirectly linked,
  broken link, library override) isn't really clear.
* Unusual behavior: Some of the icon buttons allow Shift or Ctrl clicking to
  invoke alternative behaviors. This is not a usual pattern in Blender.

This patch does the following changes:

* Adds a menu to the right of the name button to access all kinds of operations
  (create, delete, unlink, user management, library overrides, etc).
* Make good use of the "disabled hint" for tooltips, to explain why buttons are
  disabled. The UI team wants to establish this as a good practise.
* Use superimposed icons for duplicate and unlink, rather than extra buttons
  (uses less space, looks less distracting and is a nice + consistent design
  language).
* Remove fake user and user count button, they are available from the menu now.
* Support tooltips for superimposed icons (committed mouse hover feedback to
  master already).
* Slightly increase size of the name button - it was already a bit small
  before, and the move from real buttons to superimposed icons reduces usable
  space for the name itself.
* More clearly differentiate between duplicate and creating a new data-block.
  The latter is only available in the menu.
* Display library status icon on the left (linked, missing library, overridden,
  asset)
* Disables "Make Single User" button - in review we weren't sure if there are
  good use-cases for it, so better to see if we can remove it.

Note that I do expect some aspects of this design to change still. I think some
changes are problematic, but others disagreed. I will open a feedback thread on
devtalk to see what others think.

Differential Revision: https://developer.blender.org/D8554

Reviewed by: Bastien Montagne

Design discussed and agreed on with the UI team, also see T79959.

source/blender/editors/space_node/drawnode.c

@@ -771,6 +771,7 @@ static void node_shader_buts_tex_image(uiLayout *layout, bContext *C, PointerRNA
                ptr,
                "image",
                "IMAGE_OT_new",
+               NULL,
                "IMAGE_OT_open",
                NULL,
                UI_TEMPLATE_ID_FILTER_ALL,
@@ -808,6 +809,7 @@ static void node_shader_buts_tex_environment(uiLayout *layout, bContext *C, Poin
                ptr,
                "image",
                "IMAGE_OT_new",
+               NULL,
                "IMAGE_OT_open",
                NULL,
                UI_TEMPLATE_ID_FILTER_ALL,
@@ -1395,6 +1397,7 @@ static void node_composit_buts_image(uiLayout *layout, bContext *C, PointerRNA *
                ptr,
                "image",
                "IMAGE_OT_new",
+               NULL,
                "IMAGE_OT_open",
                NULL,
                UI_TEMPLATE_ID_FILTER_ALL,
@@ -1426,7 +1429,8 @@ static void node_composit_buts_viewlayers(uiLayout *layout, bContext *C, Pointer
   bNode *node = ptr->data;
   uiLayout *col, *row;
 
-  uiTemplateID(layout, C, ptr, "scene", NULL, NULL, NULL, UI_TEMPLATE_ID_FILTER_ALL, false, NULL);
+  uiTemplateID(
+      layout, C, ptr, "scene", NULL, NULL, NULL, NULL, UI_TEMPLATE_ID_FILTER_ALL, false, NULL);
 
   if (!node->id) {
     return;
@@ -1548,7 +1552,8 @@ static void node_composit_buts_defocus(uiLayout *layout, bContext *C, PointerRNA
   col = uiLayoutColumn(layout, false);
   uiItemR(col, ptr, "use_preview", DEFAULT_FLAGS, NULL, ICON_NONE);
 
-  uiTemplateID(layout, C, ptr, "scene", NULL, NULL, NULL, UI_TEMPLATE_ID_FILTER_ALL, false, NULL);
+  uiTemplateID(
+      layout, C, ptr, "scene", NULL, NULL, NULL, NULL, UI_TEMPLATE_ID_FILTER_ALL, false, NULL);
 
   col = uiLayoutColumn(layout, false);
   uiItemR(col, ptr, "use_zbuffer", DEFAULT_FLAGS, NULL, ICON_NONE);
@@ -2163,8 +2168,17 @@ static void node_composit_buts_ycc(uiLayout *layout, bContext *UNUSED(C), Pointe
 
 static void node_composit_buts_movieclip(uiLayout *layout, bContext *C, PointerRNA *ptr)
 {
-  uiTemplateID(
-      layout, C, ptr, "clip", NULL, "CLIP_OT_open", NULL, UI_TEMPLATE_ID_FILTER_ALL, false, NULL);
+  uiTemplateID(layout,
+               C,
+               ptr,
+               "clip",
+               NULL,
+               NULL,
+               "CLIP_OT_open",
+               NULL,
+               UI_TEMPLATE_ID_FILTER_ALL,
+               false,
+               NULL);
 }
 
 static void node_composit_buts_movieclip_ex(uiLayout *layout, bContext *C, PointerRNA *ptr)
@@ -2172,8 +2186,17 @@ static void node_composit_buts_movieclip_ex(uiLayout *layout, bContext *C, Point
   bNode *node = ptr->data;
   PointerRNA clipptr;
 
-  uiTemplateID(
-      layout, C, ptr, "clip", NULL, "CLIP_OT_open", NULL, UI_TEMPLATE_ID_FILTER_ALL, false, NULL);
+  uiTemplateID(layout,
+               C,
+               ptr,
+               "clip",
+               NULL,
+               NULL,
+               "CLIP_OT_open",
+               NULL,
+               UI_TEMPLATE_ID_FILTER_ALL,
+               false,
+               NULL);
 
   if (!node->id) {
     return;
@@ -2188,8 +2211,17 @@ static void node_composit_buts_stabilize2d(uiLayout *layout, bContext *C, Pointe
 {
   bNode *node = ptr->data;
 
-  uiTemplateID(
-      layout, C, ptr, "clip", NULL, "CLIP_OT_open", NULL, UI_TEMPLATE_ID_FILTER_ALL, false, NULL);
+  uiTemplateID(layout,
+               C,
+               ptr,
+               "clip",
+               NULL,
+               NULL,
+               "CLIP_OT_open",
+               NULL,
+               UI_TEMPLATE_ID_FILTER_ALL,
+               false,
+               NULL);
 
   if (!node->id) {
     return;
@@ -2214,8 +2246,17 @@ static void node_composit_buts_moviedistortion(uiLayout *layout, bContext *C, Po
 {
   bNode *node = ptr->data;
 
-  uiTemplateID(
-      layout, C, ptr, "clip", NULL, "CLIP_OT_open", NULL, UI_TEMPLATE_ID_FILTER_ALL, false, NULL);
+  uiTemplateID(layout,
+               C,
+               ptr,
+               "clip",
+               NULL,
+               NULL,
+               "CLIP_OT_open",
+               NULL,
+               UI_TEMPLATE_ID_FILTER_ALL,
+               false,
+               NULL);
 
   if (!node->id) {
     return;
@@ -2538,7 +2579,8 @@ static void node_composit_buts_mask(uiLayout *layout, bContext *C, PointerRNA *p
 {
   bNode *node = ptr->data;
 
-  uiTemplateID(layout, C, ptr, "mask", NULL, NULL, NULL, UI_TEMPLATE_ID_FILTER_ALL, false, NULL);
+  uiTemplateID(
+      layout, C, ptr, "mask", NULL, NULL, NULL, NULL, UI_TEMPLATE_ID_FILTER_ALL, false, NULL);
   uiItemR(layout, ptr, "use_feather", DEFAULT_FLAGS, NULL, ICON_NONE);
 
   uiItemR(layout, ptr, "size_source", DEFAULT_FLAGS, "", ICON_NONE);
@@ -2559,7 +2601,8 @@ static void node_composit_buts_keyingscreen(uiLayout *layout, bContext *C, Point
 {
   bNode *node = ptr->data;
 
-  uiTemplateID(layout, C, ptr, "clip", NULL, NULL, NULL, UI_TEMPLATE_ID_FILTER_ALL, false, NULL);
+  uiTemplateID(
+      layout, C, ptr, "clip", NULL, NULL, NULL, NULL, UI_TEMPLATE_ID_FILTER_ALL, false, NULL);
 
   if (node->id) {
     MovieClip *clip = (MovieClip *)node->id;
@@ -2595,8 +2638,17 @@ static void node_composit_buts_trackpos(uiLayout *layout, bContext *C, PointerRN
 {
   bNode *node = ptr->data;
 
-  uiTemplateID(
-      layout, C, ptr, "clip", NULL, "CLIP_OT_open", NULL, UI_TEMPLATE_ID_FILTER_ALL, false, NULL);
+  uiTemplateID(layout,
+               C,
+               ptr,
+               "clip",
+               NULL,
+               NULL,
+               "CLIP_OT_open",
+               NULL,
+               UI_TEMPLATE_ID_FILTER_ALL,
+               false,
+               NULL);
 
   if (node->id) {
     MovieClip *clip = (MovieClip *)node->id;
@@ -2636,8 +2688,17 @@ static void node_composit_buts_planetrackdeform(uiLayout *layout, bContext *C, P
   bNode *node = ptr->data;
   NodePlaneTrackDeformData *data = node->storage;
 
-  uiTemplateID(
-      layout, C, ptr, "clip", NULL, "CLIP_OT_open", NULL, UI_TEMPLATE_ID_FILTER_ALL, false, NULL);
+  uiTemplateID(layout,
+               C,
+               ptr,
+               "clip",
+               NULL,
+               NULL,
+               "CLIP_OT_open",
+               NULL,
+               UI_TEMPLATE_ID_FILTER_ALL,
+               false,
+               NULL);
 
   if (node->id) {
     MovieClip *clip = (MovieClip *)node->id;
@@ -3072,6 +3133,7 @@ static void node_texture_buts_image(uiLayout *layout, bContext *C, PointerRNA *p
                ptr,
                "image",
                "IMAGE_OT_new",
+               NULL,
                "IMAGE_OT_open",
                NULL,
                UI_TEMPLATE_ID_FILTER_ALL,