Refactor exporting NeMo models (#2362)

Refactors and extends model export support to include new NeMo Parakeet TDT int8 variants for English and Japanese, updating the Kotlin API, export scripts, test runners, and CI workflows.

- Added support for two new int8 model types in OfflineRecognizer.kt.
- Enhanced Python export scripts to perform dynamic quantization and metadata injection.
- Updated shell scripts and GitHub workflows to package, test, and publish int8 model artifacts.

scripts/nemo/parakeet-tdt_ctc-0.6b-ja/run-ctc.sh

@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+
+set -ex
+
+python3 ./export-onnx-ctc.py
+
+ls -lh *.onnx
+
+mkdir -p test_wavs
+pushd test_wavs
+curl -SL -O https://huggingface.co/csukuangfj/reazonspeech-k2-v2-ja-en/resolve/main/test_wavs/transcripts.txt
+curl -SL -O https://hf-mirror.com/csukuangfj/reazonspeech-k2-v2-ja-en/resolve/main/test_wavs/test_ja_1.wav
+curl -SL -O https://hf-mirror.com/csukuangfj/reazonspeech-k2-v2-ja-en/resolve/main/test_wavs/test_ja_2.wav
+popd
+
+d=sherpa-onnx-nemo-parakeet-tdt_ctc-0.6b-ja-35000-int8
+
+mkdir -p $d
+mv -v model.int8.onnx $d/
+cp -v tokens.txt $d/
+cp -av test_wavs $d
+ls -lh $d
+
+
+d=sherpa-onnx-nemo-parakeet-tdt_ctc-0.6b-ja-35000-int8
+python3 ./test-onnx-ctc-non-streaming.py \
+  --model $d/model.int8.onnx \
+  --tokens $d/tokens.txt \
+  --wav $d/test_wavs/test_ja_1.wav
+
+python3 ./test-onnx-ctc-non-streaming.py \
+  --model $d/model.int8.onnx \
+  --tokens $d/tokens.txt \
+  --wav $d/test_wavs/test_ja_2.wav