0c tab capture - enable tests on Windows

Major changes:
- Implement HostGpuMemoryBufferManager::CopyGpuMemoryBufferSync(),
  introduce thread-hop to CopyGpuMemoryBufferAsync() if required.
- Introduce a receiver thread in FakeVideoCaptureStack. This is needed
  for Windows, since on Windows, mapping GMBs incurs a mojom call from
  a synchronous function. This means that the thread that attempts to
  map the GMB will be blocked waiting for the response. If it so
  happens that this is also the thread that processes IPC responses,
  it'd cause a deadlock.
- Add the thread-hopping required so that FakeVideoCaptureStackReceiver
  can call into FakeVideoCaptureStack that owns it.
- FakeVideoStackReceiver can now map GMBs on Windows.
- Instantiate NV12 variant of the
  WebContentsVideoCaptureDeviceBrowserTest on Windows.

Change-Id: Ie38038a039d8389f1307ceb174b836437ff79fb5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4021530
Reviewed-by: Alexander Cooper <alcooper@chromium.org>
Commit-Queue: Piotr Bialecki <bialpio@chromium.org>
Reviewed-by: Vasiliy Telezhnikov <vasilyt@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1089946}