add SetRate to nvenc encoder implementations

[chenosaurus]

• NVENC encoders were not correctly updating encode bitrate and was stuck at the initial rate set by webrtc, this fixes the problem by properly implementing SetRate on the encoder implementation to properly handle requests to change encode config.

[Copilot]

Pull request overview

This PR fixes NVENC-based encoders not applying runtime bitrate updates from WebRTC by adding an NvEncoder::SetRates(...) helper that reconfigures an active NVENC session, and wiring WebRTC SetRates(...) calls to invoke it.

Changes:

• Add NvEncoder::SetRates(frameRate, averageBitrate) to reconfigure NVENC encode parameters during a live session.
• Call encoder_->SetRates(...) from the H264/H265/AV1 encoder implementations when WebRTC updates rate control parameters.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
webrtc-sys/src/nvidia/NvCodec/NvCodec/NvEncoder/NvEncoder.h	Adds the SetRates(...) API to the NVENC wrapper class.
webrtc-sys/src/nvidia/NvCodec/NvCodec/NvEncoder/NvEncoder.cpp	Implements SetRates(...) via NVENC reconfigure using current initialize params and updated RC settings.
webrtc-sys/src/nvidia/h265_encoder_impl.cpp	Invokes NVENC SetRates(...) during WebRTC rate updates for H265.
webrtc-sys/src/nvidia/h264_encoder_impl.cpp	Invokes NVENC SetRates(...) during WebRTC rate updates for H264.
webrtc-sys/src/nvidia/av1_encoder_impl.cpp	Invokes NVENC SetRates(...) during WebRTC rate updates for AV1.

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