Let the send queue generate callbacks directly. No functional change - pure refactoring. Bug: webrtc:5696 Change-Id: Ic1e8ccba9612c5955e599c5d8257a5fa6980f666 Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/264143 Reviewed-by: Florent Castelli <orphis@webrtc.org> Commit-Queue: Victor Boivie <boivie@webrtc.org> Cr-Commit-Position: refs/heads/main@{#37401}