Initialize more RtpSender parameters via the constructor

Initialize stream_ids, init_send_encodings, and send_codecs in
AudioRtpSender and VideoRtpSender at construction time. This avoids
post-creation signaling-thread state updates via ConfigureSender and
ConfigureSendCodecs, simplifying the transceiver creation flow and
improving memory and thread safety.

Bug: none
Change-Id: I9bb52538f5d98936d8c32f12905c8c5cadfd99f2
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/474940
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#47807}