Address a shader that uses the same texture as both a GL texture
(e.g. using a sampler) AND as a GL image (e.g. using imageLoad or
imageStore).  The barrier and descriptor set created by
ContextVk::handleDirtyTexturesImpl() are wrong (read-only).  This is
fixed by having ContextVk::handleDirtyTexturesImpl() look up if the
image is also being used as an image texture, and if so, use the
layout that should be used in that case.

Bug: angleproject:4413
Change-Id: I75684e1cfc7ed74296802ab6e31468d81625d4a5
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2099311
Commit-Queue: Ian Elliott <ianelliott@google.com>
Reviewed-by: Cody Northrop <cnorthrop@google.com>