Right now color render target's image's layout change are done at
beginRenderPass time. The problem is that the layout also depends on
whether texture is also being used as a sampler or not. That information
is not known when renderpass starts. We did some special treatment for
depth stencil attachment so that its layout determination is deferred
until endRenderPass time. This CL expands that same mechanism to color
attachment as well. Right now the color attachment will still pick the
same ImageLayout::ColorAttachment layout since the logic to detect it is
also used for texture sampling is not there yet.

Bug: b/175584609
Change-Id: Id7486174d475f894461578b31d0d40fdd90e808a
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2744121Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Charlie Lao <cclao@google.com>