Removes the only remaining dependency on sequence number in NetEq except for the NackTracker (which arguably doesn't belong in NetEq). This fixes a potential issue where FEC is not perfectly aligned with the original packet boundaries, causing both the FEC and the original packet to be decoded. Bug: webrtc:13322 Change-Id: I3abec9ebfc194976fca42d5f4f4ed4ee136f44ef Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/300560 Reviewed-by: Henrik Lundin <henrik.lundin@webrtc.org> Commit-Queue: Jakob Ivarsson <jakobi@webrtc.org> Cr-Commit-Position: refs/heads/main@{#39815}