VSE: Image transform tools

Add tools for image manipulation in sequencer preview region.

This includes:
- Translate, rotate and resize operators, tools and gizmos
- Origin for image transformation
- Median point and individual origins pivot modes
- Select and Box select operator works in preview
- Image overlay drawing

ref T90156

Reviewed By: campbellbarton

Differential Revision: https://developer.blender.org/D12105

source/blender/editors/transform/transform.c

@@ -1703,11 +1703,13 @@ bool initTransform(bContext *C, TransInfo *t, wmOperator *op, const wmEvent *eve
     t->draw_handle_cursor = WM_paint_cursor_activate(
         SPACE_TYPE_ANY, RGN_TYPE_ANY, transform_draw_cursor_poll, transform_draw_cursor_draw, t);
   }
-  else if (t->spacetype == SPACE_SEQ) {
-    t->draw_handle_view = ED_region_draw_cb_activate(
-        t->region->type, drawTransformView, t, REGION_DRAW_POST_VIEW);
-  }
-  else if (ELEM(t->spacetype, SPACE_IMAGE, SPACE_CLIP, SPACE_NODE, SPACE_GRAPH, SPACE_ACTION)) {
+  else if (ELEM(t->spacetype,
+                SPACE_IMAGE,
+                SPACE_CLIP,
+                SPACE_NODE,
+                SPACE_GRAPH,
+                SPACE_ACTION,
+                SPACE_SEQ)) {
     t->draw_handle_view = ED_region_draw_cb_activate(
         t->region->type, drawTransformView, t, REGION_DRAW_POST_VIEW);
     t->draw_handle_cursor = WM_paint_cursor_activate(