Vulkan: Move overlay draw after swap's implicit flush While this introduces a render pass for drawing the overlay, it isolates it from the rest of code associated with the implicit flush on swap and relevant optimizations. This makes the overlay counters more accurate when it comes to said optimizations. Bug: angleproject:7084 Change-Id: I3298612923fe07139891a4252cd2a88de1783ee7 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3602839 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Amirali Abdolrashidi <abdolrashidi@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>