[TTS][ASR] customize arguments for trimming the leading/trailing silence

[XuesongYang]

What does this PR do ?

It supports overriding arguments of librosa.effects.trim when trimming silence. By default, we assign trim: false in YAML config. But when enabling it by trim: true, you have options to override original arguments of librosa.effects.trim, for example,

 trim: true
  trim_top_db: 50,
  trim_frame_length: ${model.n_window_size},
  trim_hop_length: ${model.n_window_stride},

Collection: [Note which collection this PR will affect]

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# Add a code snippet demonstrating how to use this 

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[titu1994]

Overall looks fine, I will leave to Ryan for final review

[rlangman]

Looks good to me. Thanks for adding this.

[redoctopus]

LGTM