UI: Update default mask icon

Based on the design of #102585, This PR replaces the MOD_MASK icon with
the CLIP_UVDEHLT icon to better communicate the intent of masking across
many areas of Blender. It also changes the Grease Pencil `invert` icons
to avoid conflicts with the CLIPUV_DEHLT & CLIPUV_HLT.

Pull Request: https://projects.blender.org/blender/blender/pulls/117467

source/blender/makesrna/intern/rna_gpencil_legacy.cc

@@ -1969,7 +1969,7 @@ static void rna_def_gpencil_layer_mask(BlenderRNA *brna)
 
   prop = RNA_def_property(srna, "invert", PROP_BOOLEAN, PROP_NONE);
   RNA_def_property_boolean_sdna(prop, nullptr, "flag", GP_MASK_INVERT);
-  RNA_def_property_ui_icon(prop, ICON_CLIPUV_HLT, -1);
+  RNA_def_property_ui_icon(prop, ICON_SELECT_INTERSECT, -1);
   RNA_def_property_ui_text(prop, "Invert", "Invert mask");
   RNA_def_property_update(prop, NC_GPENCIL | ND_DATA, "rna_GPencil_update");
 }