Vulkan: Allow depth and stencil resolve to be separately added In preparation for optimizing resolve through glBlitFramebuffer for depth/stencil attachments. Bug: angleproject:7551 Change-Id: I57650d82c0cc6e56f44591eadfc42ac794cfef09 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5399140 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Amirali Abdolrashidi <abdolrashidi@google.com> Reviewed-by: Yuxin Hu <yuxinhu@google.com>