Refactor kokoro export (#2302)

- generate samples for https://k2-fsa.github.io/sherpa/onnx/tts/all/
- provide int8 model for kokoro v0.19 kokoro-int8-en-v0_19.tar.bz2

scripts/kokoro/v0.19/add_meta_data.py

@@ -0,0 +1,77 @@
+#!/usr/bin/env python3
+# Copyright    2025  Xiaomi Corp.        (authors: Fangjun Kuang)
+
+
+import argparse
+
+import onnx
+import torch
+
+from generate_voices_bin import speaker2id
+
+
+def get_args():
+    parser = argparse.ArgumentParser()
+    parser.add_argument(
+        "--model", type=str, required=True, help="input and output onnx model"
+    )
+
+    return parser.parse_args()
+
+
+def main():
+    args = get_args()
+    print(args.model)
+
+    model = onnx.load(args.model)
+
+    style = torch.load(
+        "./kLegacy/v0.19/voices/af.pt", weights_only=True, map_location="cpu"
+    )
+
+    speaker2id_str = ""
+    id2speaker_str = ""
+    sep = ""
+    for s, i in speaker2id.items():
+        speaker2id_str += f"{sep}{s}->{i}"
+        id2speaker_str += f"{sep}{i}->{s}"
+        sep = ","
+
+    meta_data = {
+        "model_type": "kokoro",
+        "language": "English",
+        "has_espeak": 1,
+        "sample_rate": 24000,
+        "version": 1,
+        "voice": "en-us",
+        "style_dim": ",".join(map(str, style.shape)),
+        "n_speakers": len(speaker2id),
+        "speaker2id": speaker2id_str,
+        "id2speaker": id2speaker_str,
+        "speaker_names": ",".join(map(str, speaker2id.keys())),
+        "model_url": "https://huggingface.co/hexgrad/kLegacy/",
+        "see_also": "https://huggingface.co/spaces/hexgrad/Kokoro-TTS",
+        "maintainer": "k2-fsa",
+        "comment": "This is kokoro v0.19 and supports only English",
+    }
+
+    print(model.metadata_props)
+
+    while len(model.metadata_props):
+        model.metadata_props.pop()
+
+    for key, value in meta_data.items():
+        meta = model.metadata_props.add()
+        meta.key = key
+        meta.value = str(value)
+    print("--------------------")
+
+    print(model.metadata_props)
+
+    onnx.save(model, args.model)
+
+    print(f"Please see {args.model}, ./voices.bin, and ./tokens.txt")
+
+
+if __name__ == "__main__":
+    main()