gpu: Cache DXGI shared handle state across shared image mailboxes

Augment DXGI GpuMemoryBuffer handles with a base::UnguessableToken that
can be used to identify the GMB after its duplicated. The DXGI shared
handle is not sufficient for this purpose since D3D/Windows provides no
way to retrieve a unique identifier from a handle.

DXGISharedHandleManager caches shared handle state using the token as
key and vends out scoped_refptrs to the shared handle state. This allows
multiple shared images, created from duplicated handles that refer to
the same texture, to share keyed mutex state which prevents them from
causing accidental deadlocks. DXGISharedHandleManager itself is
ref-counted, thread-safe, and outlives the shared handle state.

The existing shared handle tests are updated to test this functionality
and new unit tests for DXGISharedHandleManager are also added.

Bug: 1252296
Change-Id: I3a01810b3d3fa52296aea5fa221ba3ad1c0714ae
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3198119
Reviewed-by: danakj <danakj@chromium.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@chromium.org>
Reviewed-by: Frank Liberato <liberato@chromium.org>
Reviewed-by: Robert Kroeger <rjkroege@chromium.org>
Reviewed-by: Rafael Cintron <rafael.cintron@microsoft.com>
Commit-Queue: Sunny Sachanandani <sunnyps@chromium.org>
Cr-Commit-Position: refs/heads/main@{#933953}