webrtc: Expose CaptureCompressionGain and GainController1 config for Java

[XiaWuSharve]

This CL exposes the capture compression gain and GainController1
configuration APIs to the Java layer via ExternalAudioProcessingFactory.

Previously, these AGC parameters were not configurable from Java,
making it difficult to tune audio processing for specific communication
scenarios.

Changes:

• Add setCaptureCompressionGain() to runtime adjust compression gain.
• Add enableGainController1() with Agc1Mode enum to configure mode,
  target level, compression gain, and limiter.
• Implement native JNI bindings in external_audio_processing_factory.cc.
• Add logging in AudioProcessingImpl to track runtime setting handling.

Bug: None
Test: Manually tested with GetStream's WebRTC build

[coderabbitai]

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