Bug 1822194 - Vendor libwebrtc from 75170be4ac

We already cherry-picked this when we vendored d8c4de7172.

Upstream commit: https://webrtc.googlesource.com/src/+/75170be4acc90fece7c65f1a5b9bef03a5cc3880
    Revert "Remame VideoSendStream::UpdateActiveSimulcastLayers to StartPerRtpStream"

    This reverts commit d8c4de71722c9de38f942932be21d4015f32a3bc.

    Reason for revert: Tentative revert due to possible perf regression. b/260123362

    Original change's description:
    > Remame VideoSendStream::UpdateActiveSimulcastLayers to StartPerRtpStream
    >
    > VideoSendStreamImpl::Start and VideoSendStream::Start are not used by PeerConnections, only StartPerRtpStream.
    > Therefore this cl:
    > - Change implementation of VideoSendStream::Start to use VideoSendStream::StartPerRtpStream. VideoSendstream::Start is kept for convenience.
    > - Remove VideoSendStreamImpl::Start() since it was only used by tests that use call and is confusing.
    > - RtpVideoSender::SetActive is removed/changed to RtpVideoSender::Stop(). For normal operations RtpVideoSender::SetActiveModules is used.
    >
    > Bug: none
    > Change-Id: I43b153250b07c02fe63c84e3c4cec18d4ec0d47a
    > Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/283660


    > Reviewed-by: Erik Språng <sprang@webrtc.org>
    > Commit-Queue: Per Kjellander <perkj@webrtc.org>
    > Cr-Commit-Position: refs/heads/main@{#38698}

    Bug: none
    Change-Id: I4f0d27679e51361b9ec54d2ae8e4d972527875d1
    Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/284940


    Reviewed-by: Per Kjellander <perkj@webrtc.org>
    Commit-Queue: Erik Språng <sprang@webrtc.org>
    Auto-Submit: Per Kjellander <perkj@webrtc.org>
    Bot-Commit: rubber-stamper@appspot.gserviceaccount.com <rubber-stamper@appspot.gserviceaccount.com>
    Reviewed-by: Erik Språng <sprang@webrtc.org>
    Cr-Commit-Position: refs/heads/main@{#38725}