Let --trace-gc now also emit whether the GC is a memory reducing GC or not.

Change-Id: If0efd9e9a52d9cb861ca9692a2c93812effeabaa
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2064220Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66389}