The removal of the UNDO flag to prevent adding undo steps when using the
`paint.sample_color` operator results in the "Sample Merged" option
being inaccessible to users without them adding a keymap of their own.
This commit makes the following changes:
* For Texture Paint using the default blender keymap, the Shift-Ctrl-X
keybind is assigned to this operator with the merged option set to True
* For Texture Paint, using the industry compatible keymap, the Shift-I
keybind is assigned to this operator with the merged option set to
True
This parameter is only relevant for 3D Texture Painting so it is not
added to the other modes.
For all other `paint.sample_color` entries in both the keymap and in
some menus, the `merge` option is explicitly set to False.
Ref: #101144
Pull Request: https://projects.blender.org/blender/blender/pulls/132047
0c1ee9eba2