Vulkan: More cleanups to perf counters. This refactors the pipeline type in the ContextVk class to also use a packed enum map. It also expands the object perf counters to store both a specific and cumulative version for use in different cases. Bug: angleproject:5736 Change-Id: I6ff78e38065eb577f2b95b1d9c4f9cc31d7f325f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2774184 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>