Support Zipformer transducer ASR with whisper features. (#2321)

Adds support for Zipformer transducer ASR models that use Whisper-style 
features by introducing a new feature flag, parsing metadata, 
and integrating per-chunk normalization.

- Introduce UseWhisperFeature in the model interface and Zipformer implementation
- Parse "feature" metadata to set the whisper flag and wire it into the recognizer
- Update feature extraction logic to handle Whisper filterbanks with early returns

sherpa-onnx/csrc/online-transducer-model.h

@@ -132,6 +132,8 @@ class OnlineTransducerModel {
 
   virtual int32_t SubsamplingFactor() const { return 4; }
 
+  virtual bool UseWhisperFeature() const { return false; }
+
   virtual OrtAllocator *Allocator() = 0;
 
   Ort::Value BuildDecoderInput(