Vulkan: Add log for buffer pool stats For debugging purpose, this will calculate stats of buffer pool and output string to log. Set ANGLE_ENABLE_BUFFER_POOL_STATS_LOGGING to 1 will log stats into INFO() stream. Bug: b/230538246 Change-Id: I68f83af547e782ca7cb6cb222967ba02b8005083 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3617229 Reviewed-by: Amirali Abdolrashidi <abdolrashidi@google.com> Commit-Queue: Charlie Lao <cclao@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>