[PartitionAlloc] Add PartitionLock perftests.

Bug: 998048
Change-Id: Ic6aff1ee53ef06a770fca4570af8640b2fe5679c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3143997


Commit-Queue: Benoit L <lizeb@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/main@{#918742}