Gizmo: move transform to a persistent option

Based on feedback from animators, this is useful to keep as a view
option (as in 2.7x).

Now the transform gizmos can be enabled from the popover,
the tools still work for location/scale/rotation.
The transform tool has been removed.

See T63518

release/scripts/startup/bl_ui/space_view3d.py

@@ -4775,6 +4775,7 @@ class VIEW3D_PT_gizmo_display(Panel):
     def draw(self, context):
         layout = self.layout
 
+        scene = context.scene
         view = context.space_data
         overlay = view.overlay
 
@@ -4784,8 +4785,14 @@ class VIEW3D_PT_gizmo_display(Panel):
         col.active = view.show_gizmo
         colsub = col.column()
         colsub.prop(view, "show_gizmo_navigate", text="Navigate")
-        colsub.prop(view, "show_gizmo_context", text="Active Object")
         colsub.prop(view, "show_gizmo_tool", text="Active Tools")
+        colsub.prop(view, "show_gizmo_context", text="Active Object")
+
+        col.label(text="Transform Gizmos")
+        rowsub = col.row()
+        rowsub.active = view.show_gizmo_context
+        rowsub.prop(view, "show_gizmo_transform")
+        col.prop(scene.transform_orientation_slots[1], "type", text="")
 
 
 class VIEW3D_PT_overlay(Panel):