Previously we regenerated TextureSerial on Texture state changes such
as base/max level changes. This caused ANGLE to update descriptor sets
even though it was using the same image view handles. This change
instead uses an ImageViewSubresourceSerial which includes both a
serial for the ImageView and a 32-bit packed subresource range. The CL
speeds up NBA2k because ANGLE no longer writes new descriptors
for Texture max level changes. Local testing showed up to a 40% speedup.

Also adds a regression test with a counter for the number of descriptor
set writes in a frame.

This change will also be useful in upcoming changes that track Image
serials in the RenderPass.

Bug: angleproject:4911
Change-Id: I66249634aa56288079acf2c0eb8aa3391103533c
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2333396
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Reviewed-by: Tim Van Patten <timvp@google.com>