Fix #124674: Missing UI update exiting palette color picking

Color picker supports palette color picking by clicking during the modal
operator, but it will set initial color on the color property when
exiting from palette color picking, but it didn't send out a notifier
which means interface would kept showing last hovering color.

This fix also included a more obvious visual notification on the bottom
bar so the mode change gets more attention and would be harder to miss.

-------

This PR makes it so that if you clicked while holding `Shift + X`, this info would prompt on the bottom bar, this may need interface to look & decide whether that's needed because previously the string change wasn't eye-catchy enough:

<img width="194" alt="图片" src="attachments/5185f05a-54c2-45b9-acf9-3a0da8d686bb">

Pull Request: https://projects.blender.org/blender/blender/pulls/128842

source/blender/editors/sculpt_paint/paint_image.cc

@@ -44,6 +44,7 @@
 #include "BKE_node_runtime.hh"
 #include "BKE_object.hh"
 #include "BKE_paint.hh"
+#include "BKE_report.hh"
 #include "BKE_scene.hh"
 
 #include "NOD_texture.h"
@@ -740,6 +741,7 @@ static wmOperatorStatus sample_color_modal(bContext *C, wmOperator *op, const wm
     if (data->sample_palette) {
       BKE_brush_color_set(scene, paint, brush, data->initcolor);
       RNA_boolean_set(op->ptr, "palette", true);
+      WM_event_add_notifier(C, NC_BRUSH | NA_EDITED, brush);
     }
     WM_cursor_modal_restore(CTX_wm_window(C));
     MEM_delete(data);
@@ -769,6 +771,7 @@ static wmOperatorStatus sample_color_modal(bContext *C, wmOperator *op, const wm
         if (!data->sample_palette) {
           data->sample_palette = true;
           sample_color_update_header(data, C);
+          BKE_report(op->reports, RPT_INFO, "Sampling color for pallette");
         }
         WM_event_add_notifier(C, NC_BRUSH | NA_EDITED, brush);
       }