perf tests: Record perf counter metrics. This adds a new command line argument that will allow the user to specify perf counters to record into the test output. Bug: angleproject:4918 Change-Id: Ia7432ff96eadf13ef681f67d2d503d00fd83e06e Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3516970 Reviewed-by: Lingfeng Yang <lfy@google.com> Reviewed-by: Charlie Lao <cclao@google.com> Reviewed-by: Yuxin Hu <yuxinhu@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org>