Remove frame references in corruption detection on frame drops.

The `FrameInstrumentationGenerator` needs both the raw input frame (in
order to do sampling) and the corresponding encoded frame (in order to
map the QP to a filter size). For that reason it holds on to a small
queue of the last two input frames. This was needed in order to deal
with asynchronous encoders, especially in simulcast mode.

In webrtc:467444018 a new callback scheme was introduced where encoders
always announce when all spatial/simulcast layers are done with a frame
either through the `EncodeImage` or through a new `OnFrameDropped`
callback method.

This CL wires the new callback up through `VideoStreamEncoder` to the
`FrameInstrumentationGenerator` so that raw frame handles can be
released as soon as possible.

Bug: webrtc:467444018, webrtc:358039777
Change-Id: Icdb57bdf9c0c8efc2a3153ae204cc852e8f6cd42
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/451880
Commit-Queue: Erik Språng <sprang@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#46988}