*Scan: Start eager freeing experiment

The intent:
- Even with the StateBitmap clearing is required to guard against
transitive dangling references;
- Eager clearing avoids repetitive clearing for leaked quarantined
objects (those pointed from leaked objects).

Bug: 11297512
Change-Id: Ifce1c751ad51c7e077fb1d5503f9f28d63e6ba20
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3114931


Auto-Submit: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/main@{#914695}