Cleanup 2503 to include dev files and fixes naming

[blisc]

• Only scripts/magpietts/infer_and_evaluate.py has been tested
• All notebooks have been touched and might not work
• If using an old checkpoint, you will have to modify the config like so

if "t5_encoder" in model_cfg:
    model_cfg.encoder = model_cfg.t5_encoder
    del model_cfg.t5_encoder
if "t5_decoder" in model_cfg:
    model_cfg.decoder = model_cfg.t5_decoder
    del model_cfg.t5_decoder

• To merge on top of the current branch, it would be easiest to find where your branch deviates from https://github.com/paarthneekhara/NeMo/tree/experimentalt5tts_finalizedtransformer and then git cherry-pick one commit at a time. If you have lots of commits, make a squash merge into experimentalt5tts_finalizedtransformer and then cherry-pick the one commit