Change Blink's GarbageCollection monorail component

The new component will be Blink>GarbageCollection and not be nested
under MemoryAllocators.

Change-Id: I701c7095099b75a7c03df1f8261aa43d8d8b5896
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3114670


Commit-Queue: Kentaro Hara <haraken@chromium.org>
Auto-Submit: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/main@{#914694}