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/features.cc

@@ -131,10 +131,13 @@ class FeatureExtractor::Impl {
     std::lock_guard<std::mutex> lock(mutex_);
     if (fbank_) {
       fbank_->InputFinished();
+      return;
     } else if (whisper_fbank_) {
       whisper_fbank_->InputFinished();
+      return;
     } else if (mfcc_) {
       mfcc_->InputFinished();
+      return;
     }
 
     SHERPA_ONNX_LOGE("unreachable code");