Report the allocated size of global handles in GetHeapStatistics as
well, not including free handles.

Bug: chromium:1060192
Change-Id: I1aedba36735f897cd8518edbb5ef2261cc348bff
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2093493
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66651}