Add support for potentially out-of-order removals of packets, using a vector of sequence numbers that have been acknowledges as received. Additionally, make kStoreAndCull storage method by default with a field-trial kill-switch if things go wrong unexpectedly. Bug: webrtc:8975 Change-Id: I6da8b92d85fc362c12db82976f115626cb1d32d4 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/134307 Reviewed-by: Åsa Persson <asapersson@webrtc.org> Commit-Queue: Erik Språng <sprang@webrtc.org> Cr-Commit-Position: refs/heads/master@{#27850}