Vulkan: Finish implementation of the copySubImage - Enables all dEQP tests left for copySubImage. Bug: angleproject:2501 Change-Id: I8ae301a94e9039f24e0a20b8fd4afdf7e65659f7 Reviewed-on: https://chromium-review.googlesource.com/1057904 Commit-Queue: Luc Ferron <lucferron@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>