[TTS][DE] Multi-speaker fastpitch model training recipe on HUI-Audio-Corpus-German
# What does this PR do ?
* created a dataset preparation recipe for HUI-ACG.
    * re-write `get_data.py` to support multiprocessing and decouple text normalization. 
* added a script to convert graphemes into phonemes.
* created a model config for multi-speaker Fastpitch model training.
 

**Collection**: [Note which collection this PR will affect]

# Changelog 
- Add specific line by line info of high level changes in this PR.

# Usage
* You can potentially add a usage example below

```bash
# Download the dataset, normalize texts, create train/val/test splits of JSON manifests.
$ python scripts/dataset_processing/tts/hui_acg/get_data.py \
        --data-root /home/xueyang/datasets \
        --normalize-text
$ ls /home/xueyang/datasets/HUI-Audio-Corpus-German-clean/*_text_normed.json
test_manifest_text_normed.json  train_manifest_text_normed.json  val_manifest_text_normed.json

# run phonemizer to convert graphemes into phonemes, resulting in new files with name like train_manifest_text_normed_phonemes.json
$ python scripts/dataset_processing/tts/hui_acg/phonemizer.py \
        --json-manifests /home/xueyang/datasets/HUI-Audio-Corpus-German-clean/train_manifest_text_normed.json \
                                     /home/xueyang/datasets/HUI-Audio-Corpus-German-clean/val_manifest_text_normed.json \
                                     /home/xueyang/datasets/HUI-Audio-Corpus-German-clean/test_manifest_text_normed.json \
        --preserve-punctuation
$ ls /home/xueyang/datasets/HUI-Audio-Corpus-German-clean/*_phonemes.json
test_manifest_text_normed_phonemes.json  train_manifest_text_normed_phonemes.json  val_manifest_text_normed_phonemes.json

$ python scripts/dataset_processing/tts/extract_sup_data.py \
        --config-path hui_acg/ds_conf \
        --config-name ds_for_fastpitch_align.yaml \
        manifest_filepath=/home/xueyang/datasets/HUI-Audio-Corpus-German-clean/Friedrich_Clean/train_manifest_text_normed_phonemes.json \
        sup_data_path=/home/xueyang/datasets/HUI-Audio-Corpus-German-clean/sup_data_phonemes

# you would see the information in the terminal
-- Set up ENVs...
a867b5ef4cd08fe0db216937b2d3e767fe71b3e7
-- Started ...
[NeMo I 2022-06-17 15:15:57 tokenize_and_classify:81] Creating ClassifyFst grammars. This might take some time...
[NeMo I 2022-06-17 15:16:15 data:186] Loading dataset from /data/HUI-Audio-Corpus-German-clean/train_manifest_text_normed_phonemes.json.
[NeMo I 2022-06-17 15:16:22 data:221] Loaded dataset with 173622 files.
[NeMo I 2022-06-17 15:16:22 data:223] Dataset contains 403.30 hours.
[NeMo I 2022-06-17 15:16:22 data:321] Pruned 0 files. Final dataset contains 173622 files
[NeMo I 2022-06-17 15:16:22 data:323] Pruned 0.00 hours. Final dataset contains 403.30 hours.
Processing /home/xueyang/datasets/HUI-Audio-Corpus-German-clean/train_manifest_text_normed_phonemes.json:
PITCH_MEAN=155.3916473388672, PITCH_STD=102.26656341552734
PITCH_MIN=65.4063949584961, PITCH_MAX=2093.004638671875

# train FastPitch model. copy & paste PITCH_MEAN, PITCH_STD, PITCH_MIN, and PITCH_MAX to the params.
$ python examples/tts/fastpitch.py \
        --config-path conf/de \
        --config-name fastpitch_align_44100 \
        model.train_ds.dataloader_params.num_workers=16 \
        model.validation_ds.dataloader_params.num_workers=16 \
        model.train_ds.dataloader_params.batch_size=24 \
        model.validation_ds.dataloader_params.batch_size=24 \
        train_dataset=/home/xueyang/datasets/HUI-Audio-Corpus-German-clean/train_manifest_text_normed_phonemes.json \
        validation_datasets=/home/xueyang/datasets/HUI-Audio-Corpus-German-clean/val_manifest_text_normed_phonemes.json \
        sup_data_path=/home/xueyang/datasets/HUI-Audio-Corpus-German-clean/sup_data_phonemes \
        pitch_mean=155.3916473388672 \
        pitch_std=102.26656341552734 \
        pitch_fmin=65.4063949584961 \
        pitch_fmax=2093.004638671875 \
        trainer.devices=2 \
        trainer.num_nodes=1 \
        trainer.accumulate_grad_batches=2 \
        trainer.log_every_n_steps=10 \
        exp_manager.exp_dir=/home/xueyang/experiments/GermanTTS/multi_spk_tts_de/fastpitch-train/results \
        exp_manager.resume_if_exists=True \
        exp_manager.resume_ignore_no_checkpoint=True \
        +exp_manager.create_wandb_logger=True \
        +exp_manager.wandb_logger_kwargs.name=fastpitch-train \
        +exp_manager.wandb_logger_kwargs.project=multi_spk_tts_de 
```

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