Bring back Talk Net 2
**Describe the bug**
Talk Net 2 was deprecated but no comparable model took its place.

After experimenting with the various models, we have yet to find anything in open source land that compares to Talk Net 2. 

FastSpeech2 is *okay* but is subjectively worse (and objedtively has .25 lower MOS), especially with spacing and prosody.

Is there any reason support was dropped and the model was deprecated?

Because we have to use a very old version of NeMo to continue to support TalkNet2, it's kind of version locked us to some specific stale and conflicting dependencies within our stack.

Thanks to Pony Preservation Project, Webaverse and other open source projects, TalkNet might have been the most popular NeMo TTS model in production. There are notebooks, colab, extensive training materials built up by communities around it, for example: https://github.com/bycloudai/TalkNET-colab

Happy to make a PR, unless there are specific technical reasons why it was deprecated. In the meantime we're all living off a fork, notably this one: https://github.com/SortAnon/NeMo