Configure RtpVideoSender modules at creation

The constructor body and ConfigureSsrcs() configured the RTP modules in
several passes after rtp_streams_ had been constructed. Configure each
module right after creating it instead, with the same per-module call
order, so that rtp_streams_ is fully set up once it's constructed. This
removes ConfigureSsrcs() and most of the constructor body.

Bug: webrtc:42223727
Change-Id: I91f9329584d07fc07a9b3d1e471183387bc1cd67
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/506200
Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org>
Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#48773}