Minor improvements for webrtc fuzzers. - Send output of packetizer through depacketizer for rtp_packetizer_av1_fuzzer. - Only override payload frequency for vp8/vp9 replay fuzzers when it is zero.
<rdar://problem/118624993>
Pull request: https://github.com/WebKit/WebKit/pull/20726
Committed 271178@main (7be4320b2429): <https://commits.webkit.org/271178@main> Reviewed commits have been landed. Closing PR #20726 and removing active labels.