* Add test to Generic decoder unittests to ensure drop behaviour is covered. * Use simulated time in the generic decoder unittests. Bug: webrtc:14324 Change-Id: I10b28b45c434f92d5344683fb9ca6676efe0e08c Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/270662 Reviewed-by: Erik Språng <sprang@webrtc.org> Commit-Queue: Evan Shrubsole <eshr@webrtc.org> Cr-Commit-Position: refs/heads/main@{#37710}