MinNumObservations is set to 3 per default as loss based BWE should not be ready if it has few feedbacks. We use a flag, rather than a const since we want to customize it for our unit tests, which often have 1-2 packet feedbacks only, and customize it later in prod if necessary. Bug: webrtc:12707 Change-Id: Id1cd21aaf6137996de2e51cb5e33fc2a4bb07d8a Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/323780 Reviewed-by: Per Kjellander <perkj@webrtc.org> Commit-Queue: Diep Bui <diepbp@webrtc.org> Cr-Commit-Position: refs/heads/main@{#40952}