feat: [vLLM] Ability to use the tokenizer template

[golgeek]

Is your feature request related to a problem? Please describe.

Most models contain the template definition for the OpenAI chat endpoint in their tokenizer_config.json file on HF.
Redeclaring the template in LocalAI seems a bit counter-productive when it could be automagically applied.

Describe the solution you'd like

Model definition contains the following parameter:

template:
   use_tokenizer_template: true

If this parameter is set, on OpenAI chat endpoints (outside of the scope of functions), LocalAI doesn't even attempt to look at templating the prompt and passes the messages slice down the line to the vLLM python backend, which will apply the templating.

Additional context

PR incoming.