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/generate_voices_bin.py

@@ -0,0 +1,42 @@
+#!/usr/bin/env python3
+# Copyright    2025  Xiaomi Corp.        (authors: Fangjun Kuang)
+import torch
+from pathlib import Path
+
+
+id2speaker = {
+    0: "af",
+    1: "af_bella",
+    2: "af_nicole",
+    3: "af_sarah",
+    4: "af_sky",
+    5: "am_adam",
+    6: "am_michael",
+    7: "bf_emma",
+    8: "bf_isabella",
+    9: "bm_george",
+    10: "bm_lewis",
+}
+
+speaker2id = {speaker: idx for idx, speaker in id2speaker.items()}
+
+
+def main():
+    if Path("./voices.bin").is_file():
+        print("./voices.bin exists - skip")
+        return
+
+    with open("voices.bin", "wb") as f:
+        for _, speaker in id2speaker.items():
+            m = torch.load(
+                f"kLegacy/v0.19/voices/{speaker}.pt",
+                weights_only=True,
+                map_location="cpu",
+            ).numpy()
+            # m.shape (511, 1, 256)
+
+            f.write(m.tobytes())
+
+
+if __name__ == "__main__":
+    main()