D3D: generalize the Image2DBindLayoutCache to be per-shader. Bug: angleproject:7121 Change-Id: I3b5243583ac11a0fc96c4b9271118a8fd7ee4f66 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3550540 Reviewed-by: Jamie Madill <jmadill@chromium.org> Commit-Queue: Stephen White <senorblanco@chromium.org>