Reland of remove NV12 to I420 conversion in webrtc AV1 Encoder.

libaom supports for NV12 inputs for encoding av1 stream. It will reduce
unnecessary conversion from NV12 to I420 format.
(https://bugs.chromium.org/p/aomedia/issues/detail?id=3232&q=3232&can=2)

Original CL reviewed at https://webrtc-review.googlesource.com/c/src/+/251920

Bug: webrtc:13746
Change-Id: I96cc99674f315518d98355cb90566e78bead3e55
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/254340
Reviewed-by: Erik Språng <sprang@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36306}