This simplifies some tests and removes dependency on RtpSenderEgress for those tests in rtp_sender_unittest. Bug: webrtc:11340 Change-Id: I37489875947b0ac48a1742d2e9945510ee002f99 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/219624 Commit-Queue: Erik Språng <sprang@webrtc.org> Reviewed-by: Danil Chapovalov <danilchap@webrtc.org> Cr-Commit-Position: refs/heads/master@{#34099}