Blacklist certain LLMs from the model-list

[basetutu]

There are too many LLMs available to dig through at times.
I like to blacklist certain LLMs such that they are no longer suggested in the list.
This will allow me a quick switch between LLMs as I can better find the ones I am looking for.

We could also have a separate model list that contains the 10 last used/selected LLMs. (The number '10' could be configurable.)