Add IvfFrameReader utility class.

This CL adds a new subclass of the `FrameReader` interface, which is
used by the video codec test fixtures. It allows for reading compressed
video files in any of the supported codec types (VP8, VP9, AV1, H264*),
which is useful sometimes even if it does not directly represent a raw
video frame source.
Note that random access seeking is not supported and will crash on a
check if called.

Bug: webrtc:496266459
Change-Id: Iddc9f854194b4a0f095854fdc766dde6a5f2298d
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/465341
Commit-Queue: Erik Språng <sprang@webrtc.org>
Reviewed-by: Sergey Silkin <ssilkin@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#47483}