Add C++ runtime for vocos

[csukuangfj]

with vocos

./build/bin/sherpa-onnx-offline-tts \
  --matcha-acoustic-model=./matcha-icefall-en_US-ljspeech/model-steps-3.onnx \
  --matcha-vocoder=./vocos-22khz-univ.onnx \
  --matcha-tokens=./matcha-icefall-en_US-ljspeech/tokens.txt \
  --matcha-data-dir=./matcha-icefall-en_US-ljspeech/espeak-ng-data \
  --num-threads=1 \
  "How are you doing today? Today as always, men fall into two groups: slaves and free men. Whoever does not have two-thirds of his day for himself, is a slave, whatever he may be: a statesman, a businessman, an official, or a scholar."

/Users/fangjun/open-source/sherpa-onnx/sherpa-onnx/csrc/parse-options.cc:Read:375 ./build/bin/sherpa-onnx-offline-tts --matcha-acoustic-model=./matcha-icefall-en_US-ljspeech/model-steps-3.onnx --matcha-vocoder=./vocos-22khz-univ.onnx --matcha-tokens=./matcha-icefall-en_US-ljspeech/tokens.txt --matcha-data-dir=./matcha-icefall-en_US-ljspeech/espeak-ng-data --num-threads=1 'How are you doing today? Today as always, men fall into two groups: slaves and free men. Whoever does not have two-thirds of his day for himself, is a slave, whatever he may be: a statesman, a businessman, an official, or a scholar.'

sample=37632, progress=0.333333
sample=112260, progress=0.666667
sample=216235, progress=1.000000
Elapsed seconds: 1.930 s
Audio duration: 16.604 s
Real-time factor (RTF): 1.930/16.604 = 0.116

With hifigan_v2

./build/bin/sherpa-onnx-offline-tts \
  --matcha-acoustic-model=./matcha-icefall-en_US-ljspeech/model-steps-3.onnx \
  --matcha-vocoder=./hifigan_v2.onnx \
  --matcha-tokens=./matcha-icefall-en_US-ljspeech/tokens.txt \
  --matcha-data-dir=./matcha-icefall-en_US-ljspeech/espeak-ng-data \
  --num-threads=1 \
 "Today as always, men fall into two groups: slaves and free men. Whoever does not have two-thirds of his day for himself, is a slave, whatever he may be: a statesman, a businessman, an official, or a scholar."

/Users/fangjun/open-source/sherpa-onnx/sherpa-onnx/csrc/parse-options.cc:Read:375 ./build/bin/sherpa-onnx-offline-tts --matcha-acoustic-model=./matcha-icefall-en_US-ljspeech/model-steps-3.onnx --matcha-vocoder=./hifigan_v2.onnx --matcha-tokens=./matcha-icefall-en_US-ljspeech/tokens.txt --matcha-data-dir=./matcha-icefall-en_US-ljspeech/espeak-ng-data --num-threads=1 'Today as always, men fall into two groups: slaves and free men. Whoever does not have two-thirds of his day for himself, is a slave, whatever he may be: a statesman, a businessman, an official, or a scholar.'

sample=112568, progress=0.500000
sample=217343, progress=1.000000
Elapsed seconds: 2.315 s
Audio duration: 14.962 s
Real-time factor (RTF): 2.315/14.962 = 0.155
The text is: Today as always, men fall into two groups: slaves and free men. Whoever does not have two-thirds of his day for himself, is a slave, whatever he may be: a statesman, a businessman, an official, or a scholar.. Speaker ID: 0
Saved to ./generated.wav successfully!