Augment the resolve shaders to be able to stretch and blit too.  The
UtilsVk resolve function is accordingly expanded to include blit.

Bug: angleproject:3200
Change-Id: I30b172a5e388089735ab494f55cbfdc2781a8bf9
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1635753
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>