Vulkan: Set depthStencil loadOp to DontCare when not used and stored If depth stencil buffer is disabled during entire renderpass, and at the end of renderpass we are not storing the data back to memory, then force the loadOP to DontCare to avoid unnecessary depth stencil load or clear. Bug: b/162080462 Change-Id: I30905a6d45bec038de68e7f363ec699eb2be09ab Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2317726 Commit-Queue: Charlie Lao <cclao@google.com> Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com> Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>