PCScan: Detect and crash on double-frees

With quarantine bitmaps there is an easy way to check for double frees.
The cost is only a single extra check on the quarantined free() path.

Big thanks to the Microsoft Offensive Security Research team (Viktor
Brange, Lurene Grenier and Johnathan Norman) for suggesting the idea!

Bug: 11297512
Change-Id: I942f6807337d9929850f5d7dae6ac81d50d7084a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2725511


Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Cr-Commit-Position: refs/heads/master@{#858965}