Delete viz::SingleReleaseCallback

SingleReleaseCallback is just a wrapper around ReleaseCallback now. The
semantics for their use is the same except instead of passing around a
std::unique_ptr<SingleReleaseCallback> code can pass around a
ReleaseCallback.

Beyond the name change there are three consequences:
1. "callback->Run()" becomes "std::move(callback).Run()".
2. "SingleReleaseCallback::Create(callback)" becomes "callback".
3. Code no longer has to run then reset the callback since running a
   OnceCallback resets it. "callback = nullptr" after running can be
   deleted.

TextureDeleter relied on having heap allocated object to compare
addresses so it uses a unique_ptr<ReleaseCallback> now. There are better
ways to fix the class but it's soon to be deleted anyways.

Bug: 1200790
Change-Id: I1f85e96ce3aa9c9b7f0cf363cc6efa0d512625f3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2839349
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Reviewed-by: Jonathan Ross <jonross@chromium.org>
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Reviewed-by: Vasiliy Telezhnikov <vasilyt@chromium.org>
Commit-Queue: kylechar <kylechar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#875666}