Add explicit Windows WASAPI input AEC support

[divanshu-go]

Summary

Adds an explicit Windows-only StreamConfig::windows_input_aec flag that lets callers request endpoint Acoustic Echo Cancellation for WASAPI input streams.

When enabled for a capture endpoint, the WASAPI backend:

• sets the stream category to AudioCategory_Communications before IAudioClient::Initialize
• initializes the input stream normally
• requests IAcousticEchoCancellationControl
• passes the default communications render endpoint ID as the AEC reference, falling back to the console render endpoint

Unsupported devices continue recording normally; AEC setup is fail-open.

Details

• Defaults the flag to false from SupportedStreamConfig::config().

• Applies AEC only when the stream is a WASAPI capture/input endpoint.

• Keeps output/loopback/system-audio capture behavior unchanged.

Testing

cargo run  --example record_wav_aec -- --duration-secs 10 --output aec-recorded.wav