FEAT: Support Phi-2

[Bojun-Feng]

Fix #806

Added support for Phi-2 in GGUF and PyTorch. GGUF works as expected when tested locally. Would appreciate it if someone can test PyTorch locally as well.

Phi-2 supports a variety of input formats, so I thought the generate UI would be more appropriate.

Input formats from Hugging Face page](https://huggingface.co/microsoft/phi-2)

QA Format:
You can provide the prompt as a standalone question as follows:

Write a detailed analogy between mathematics and a lighthouse.

where the model generates the text after "." . To encourage the model to write more concise answers, you can also try the following QA format using "Instruct: \nOutput:"

Instruct: Write a detailed analogy between mathematics and a lighthouse.
Output: Mathematics is like a lighthouse. Just as a lighthouse guides ships safely to shore, mathematics provides a guiding light in the world of numbers and logic. It helps us navigate through complex problems and find solutions. Just as a lighthouse emits a steady beam of light, mathematics provides a consistent framework for reasoning and problem-solving. It illuminates the path to understanding and helps us make sense of the world around us.

where the model generates the text after "Output:".

Chat Format:

Alice: I don't know why, I'm struggling to maintain focus while studying. Any suggestions?
Bob: Well, have you tried creating a study schedule and sticking to it?
Alice: Yes, I have, but it doesn't seem to help much.
Bob: Hmm, maybe you should try studying in a quiet environment, like the library.
Alice: ...

where the model generates the text after the first "Bob:".

[aresnow1]

Is it ready for review?

[aresnow1]

I've rebased and tested on local, ready to review.