[WebRTC] Migrate from Legacy Natives to Proxy Natives

A deprecated JNI Zero syntax that we would like to migrate away from is called Legacy Natives. It is basically using the "native" keyword in Java files to specify Java->Native methods.

We would like to migrate these calls to Proxy Natives, where we are using the @NativeMethods annotation in Java files to specify Java->Native methods.

Bug: chromium:40253109
Change-Id: I11d0a5078f9784c5324ca9d7668339caf8ba0d22
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/476440
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Martin Kong <martinkong@google.com>
Reviewed-by: Zoé Lepaul <zlep@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#47978}