GHOST/Wayland: copy & paste image to clipboard support

Adds copy and paste images functionality to and from the image editor
in Linux/Wayland clipboard.

Currently the only format supported is PNG.

Ref: !119117

scripts/startup/bl_ui/space_image.py

@@ -211,7 +211,16 @@ class IMAGE_MT_image(Menu):
 
         layout.separator()
 
+        has_image_clipboard = False
         if sys.platform[:3] == "win":
+            has_image_clipboard = True
+        else:
+            from _bpy import _ghost_backend
+            if _ghost_backend() == 'WAYLAND':
+                has_image_clipboard = True
+            del _ghost_backend
+
+        if has_image_clipboard:
             layout.operator("image.clipboard_copy", text="Copy")
             layout.operator("image.clipboard_paste", text="Paste")
             layout.separator()