Keymap: Put status icons inside menu fields

Draw warning and stop icons on top of the menu fields instead.
Remove conflict views, create a new file to hold StatusMenuField
and StatusMenuItem. Set the icon with them instead.

Change-Id: If6c00199f24ac4f4fc789f12cc6cdcd7a912418f
Reviewed-on: https://review.haiku-os.org/c/haiku/+/7209
Reviewed-by: Adrien Destugues <pulkomandy@pulkomandy.tk>
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>