Vulkan: Count active renderpasses in overlay. Useful debugging information for benchmarks. Also helpful when working with the command graph to ensure we don't regress performance. Bug: angleproject:4029 Bug: angleproject:4320 Change-Id: Ibe224c40a3acaca9231bf3869486a0f8bba07ba0 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2036402 Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Tobin Ehlis <tobine@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>