Make sure gcmole detects issue in DisallowGarbageCollection scopes.

DisallowGarbageCollection is widely used in the codebase to document
code that doesn't allocate. However, this has the rather unexpected
side-effect that gcmole is not run when such a scope is active.

This CL changes the default behavior of gcmole to run even with
DisallowGarbageCollection scopes present. This will give us the best
results of both worlds, dynamic checks by the fuzzer, and static
analysis by gcmole.

To allow crazy local raw pointer operations there is a new
DisableGCMole scope that explicitly disables gcmole.

Change-Id: I0a78fb3b4ceaad35be9bcf7293d917a41f90c91f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2615419Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72039}