restricted_trace_perf: Sleep between tests option In order to get the most "real world" numbers possible, we're going to start running with clocks unlocks on Pixel devices. To avoid thermal throttling, allow for a pause between each test. Test: restricted_trace_perf.py Bug: angleproject:6970 Change-Id: If3f813cf1eadab6ea56122a3945f694eed79ed9a Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3936965 Reviewed-by: Charlie Lao <cclao@google.com> Commit-Queue: Cody Northrop <cnorthrop@google.com> Reviewed-by: Amirali Abdolrashidi <abdolrashidi@google.com>