This adds two new histograms:
- V8.MeasureMemoryDelayMilliseconds measures how long it takes to
  serve a memory measurement request
- V8.GCFinalizeMCMeasureMemory is a variant of the existing GC pause
  histogram that used when GC runs in memory measurement mode.

Additionally this CL lowers the maximum measurement delay to 10 seconds.

Bug: chromium:1049093
Change-Id: I97cbf443da514a69d6cf8c1d74d2757098e60acd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2089937Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66606}