Add OnFrameDropped stubs for remaining EncodedImageCallbacks.

This adds noop implementations for the `OnFrameDropped` method in all
implementations of EncodedImageCallback in libwebrtc. This in in
preparation of eventually making it pure virtual.

Bug: webrtc:467444018
Change-Id: Ie45255bec2dbe001de9dcab24b0222fee0514738
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/450260
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Commit-Queue: Erik Språng <sprang@webrtc.org>
Auto-Submit: Erik Språng <sprang@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#46958}