media: Remove stable.mojom.VideoFrame traits.

This CL removes the mojo traits which map stable.mojom.VideoFrame to
scoped_refptr<::media::VideoFrame>. This is in preparation to CL:4457504
which allows the OOPVideoDecoder to re-use frames previously received
from the remote decoder. Removing the traits is useful because with that
CL, not every incoming stable.mojom.VideoFrame received by the
OOPVideoDecoder will result in a media::VideoFrame, and creating a
media::VideoFrame from said stable.mojom.VideoFrame incurs in some
overhead such as consuming a strictly incrementing counter [1] and
validating the underlying GpuMemoryBufferHandle [2].

This CL moves the validation of the incoming stable.mojom.VideoFrame
from the mojo traits to the OOPVideoDecoder which is the only component
that receives them.

Functionally, this CL doesn't change much: we still create a
media::VideoFrame for every incoming stable.mojom.VideoFrame. The actual
re-use of frames is implemented in CL:4457504.

[1] https://source.chromium.org/chromium/chromium/src/+/main:media/base/video_frame.cc;l=1422;drc=269a0caf81464f39a3d54942a891652ba1f2ba40
[2] https://source.chromium.org/chromium/chromium/src/+/main:media/mojo/mojom/stable/stable_video_decoder_types_mojom_traits.cc;l=1679-1682;drc=bd1cbddfe3cbecc083674c0c9de89b2e67b2cc04

Bug: b:277832201, b:195769334
Test: video.*oopvd* on volteer
Change-Id: I50e71d84188f99ce630a75a5bc3002f75b787de5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4450245
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Andres Calderon Jaramillo <andrescj@chromium.org>
Reviewed-by: Pilar Molina Lopez <pmolinalopez@chromium.org>
Reviewed-by: Alex Gough <ajgo@chromium.org>
Code-Coverage: Findit <findit-for-me@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1135387}