Adds new histogram V8.TimeToSafepoint to measure the time needed to
reach a global safepoint/stop-the-world.

Bug: v8:10315
Change-Id: I77701b26dfd47e04d64c4ecba3c47530ff8b9485
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2308390Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68959}