Allow the embedder to decrement its allocated bytes count:
- The decrement will be applied to the used bytes value.
- The decrement is ignored for the total allocated bytes.

Bug: chromium:948807
Change-Id: I609ccf81017b693e0db13b499cbf8967f5f8a2c7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1631428
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#61982}