[M148] Always release VideoEncoders before destruction.

Original change's description:
> Always release VideoEncoders before destruction.
>
> Without a `Release()` call there is a potential for race conditions
> between asynchronous encoder callbacks and the destructor sequence.
>
> Bug: chromium:504620824
> Change-Id: I1fba23ef3a4a238503cdf8d2ea5831e815d7b902
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/465582
> Auto-Submit: Erik Språng <sprang@webrtc.org>
> Reviewed-by: Sergey Silkin <ssilkin@webrtc.org>
> Commit-Queue: Sergey Silkin <ssilkin@webrtc.org>
> Commit-Queue: Erik Språng <sprang@webrtc.org>
> Cr-Commit-Position: refs/heads/main@{#47495}

(cherry picked from commit 21d9744bd599d106da9171fbb1ed09047d7178ca)

Bug: chromium:505251595,chromium:504620824
Change-Id: I1fba23ef3a4a238503cdf8d2ea5831e815d7b902
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/468940
Auto-Submit: Chrome Cherry Picker <chrome-cherry-picker@chops-service-accounts.iam.gserviceaccount.com>
Commit-Queue: rubber-stamper@appspot.gserviceaccount.com <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: rubber-stamper@appspot.gserviceaccount.com <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/branch-heads/7778@{#7}
Cr-Branched-From: ca896b7ffef011bbf6957c99d413c5aac602c99f-refs/heads/main@{#47319}