Improve Encoder behavior when used with OBS Studio

[Xaymar]

Explain the Pull Request

• NVENC (via FFmpeg) can now properly be used for Replay Buffer and sets the requested information during obs_video_encoder_create.
• NVENC (via FFmpeg) now also respects streaming service limits, which OBS sets in a 2nd call to obs_encoder_update.
• NVENC (via FFmpeg) now supports dynamic reconfiguration for bitrate.
• AOM AV1 (direct) no longer sets packet priority and drop priority to negative values when OBS expects positive numbers.
• FFmpeg Encoders now properly set packet priority and drop priority according to the reported frame type.
• FFmpeg Encoders now properly migrate settings in OBS Studio via a work-around involving modified_properties2.
• NVENC (via FFmpeg) no longer constantly attempts to transfer settings from older versions.

Related Issues

Checklist

• I will become the maintainer for this part of code.
• I have tested this code on all supported Platforms.