media/chromeos/VDPipeline: Make FrameResourceConverter output VideoFrames

At the end of VideoDecoderPipeline a VideoFrame needs to be produced.
This was happening in OnFrameConverted. However, all implementations of
FrameResourceConverter were producing a VideoFrameResource, which were
being unwrapped in OnFrameConverted.

This changes FrameResourceConverter to output VideoFrames instead of
VideoFrameResources. VideoDecoderPipeline::OnFrameConverted() now
accepts a VideoFrame. The VideoFrame conversion code in
OnFrameConverted() has been moved into a new FrameResourceConverter
class, DefaultFrameConverter.

DefaultFrameConverter is used by VideoDecoderPipeline when a client does
not specify a converter. It uses the built-in FrameResource methods to
convert a FrameResource to a VideoFrame. VideoDecoderPipeline also drops
its support of NULL |frame_converter_| since it is guaranteed to be set.

UsesGetOriginalFrameCB() was added to FrameResourceConverter as a way
for VideoDecoderPipeline to determine whether or not it needs to use
set_get_original_frame_cb(). This fixes unit tests where the frame pool
is expected to be a PlatformVideoFramePool.

Bug: b:332382416
Change-Id: Ic78869ae287fe46654bb7d7fb046d494ed404fd5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5632235
Commit-Queue: Nathan Hebert <nhebert@chromium.org>
Reviewed-by: Andres Calderon Jaramillo <andrescj@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1319549}