Remove separate codec, HDR, and remote bitrate adjustments

We currently scale bitrate based on both remote vs local, SDR vs HDR, and H.264 vs
HEVC vs AV1. This has led to a lot of user confusion wondering why the bitrate
doesn't seem to match their selection in some configurations.

In H.264 local streams, we will currently overshoot the selected bitrate by about
20% due to FEC, while remote streams will be right around the selected bitrate due
to remote-specific FEC bitrate adjustments.

HEVC and AV1 streams (as configured by most clients) basically behave similarly
between local and remote, since the codec bitrate adjustment factor of 75% is nearly
the same as the FEC bitrate adjustment factor of 80%. However, this adjustment was
only performed for SDR streams so local HDR streams would overshoot like H.264.

This change cleans up all this mess by using a single non-codec-specific video
bitrate adjustment for FEC in all cases. It also allows Sunshine to perform the FEC
adjustment on its end if the default FEC value of 20% has been overridden by the
user or if we implement dynamic FEC support in the future.

The net result is HEVC and AV1 SDR streams will only see a tiny bitrate increase,
but HDR and H.264 may see noticable 20% bitrate reductions that may require the
user to adjust their bitrate setting to reach the effective value they got before.
However, the new behavior should be more intuitive for users going forward since
changing codecs, using a VPN, or enabling HDR won't cause significant changes to the
video bitrate.

src/Limelight-internal.h

@@ -29,7 +29,6 @@ extern bool HighQualitySurroundSupported;
 extern bool HighQualitySurroundEnabled;
 extern OPUS_MULTISTREAM_CONFIGURATION NormalQualityOpusConfig;
 extern OPUS_MULTISTREAM_CONFIGURATION HighQualityOpusConfig;
-extern int OriginalVideoBitrate;
 extern int AudioPacketDuration;
 extern bool AudioEncryptionEnabled;
 extern bool ReferenceFrameInvalidationSupported;