Some apps have a pattern where they clear the depth & stencil buffers
in the middle of the frame which causes the Vulkan backend to stop the
existing render pass and start a new one. This causes more loads &
stores of buffer contents than if we inline that clear with a draw.

Bug: b/159808300
Bug: angleproject:4695
Change-Id: I7a15af22f47a81051fa33fa19eaa123d8b66597c
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2289945
Commit-Queue: Courtney Goeltzenleuchter <courtneygo@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Charlie Lao <cclao@google.com>