Revert "Remove dead code from ModuleRtpRtcpImpl2"

This reverts commit 8d4d671e9be98a090921006cc988cc1fc4fe1947.

Reason for revert: Breaks wasm builds.



Original change's description:
> Remove dead code from ModuleRtpRtcpImpl2
> 
> Bug: webrtc:11581
> Change-Id: I70e1df2724801c1bc7fb5cfb52cb6d1d44920b0d
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/176570
> Commit-Queue: Tommi <tommi@webrtc.org>
> Reviewed-by: Erik Språng <sprang@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#31467}

TBR=tommi@webrtc.org,sprang@webrtc.org

Change-Id: I790374f7fa93147824e6fa2779a0bbaf5987924f
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: webrtc:11581
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/176746
Reviewed-by: Tommi <tommi@webrtc.org>
Commit-Queue: Tommi <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#31468}