Fix out-of-bounds write in SetupCodec due to excessive RIDs

In GetSendEncodingsFromRemoteDescription, limit the number of processed
simulcast layers to kMaxSimulcastStreams.

Added bounds checking in SetupCodec to avoid writing past the end of the
simulcastStream array.

Bug: chromium:486536241
Change-Id: Ie5bbe2bd3362cb4b319ec5be67c6288da8ad953a
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/458720
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Reviewed-by: Philipp Hancke <philipp.hancke@googlemail.com>
Commit-Queue: Tomas Gunnarsson <tommi@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#47230}