Vulkan: Add support for internal cache hit and miss counts Add a CacheStats class that provides cache hit and miss bookkeeping. All internal caches make use of this class to keep track of its stats. This provides a means to profile cache hit ratios a.k.a Vulkan object reuse for any application. Bug: angleproject:5447 Test: Manual verification with angle_end2end_tests Change-Id: I44eeb0c2b9b291ec1cdd156fb2be4a5fe80d2848 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2580111 Commit-Queue: Mohan Maiya <m.maiya@samsung.com> Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>