Support time-based LPs

[alessiodevoto]

Main proposed changes:

• added a time based trigger for TriggerPhraseLP, so that the sentence can be triggered after N seconds
• added a MaxTimeLP that exponentially increases the probability of EOS token until a max_time. Once max_time is reached, it stops generation (optionally after completing the sentence)
• these two can be used together to urge the model to answer and then stop generation

Tested on all notebooks (and trtllm test files).