[LLM] Add support for PaLM 2

[Yiannis128]

Google recently announced PaLM 2 models. ESBMC-AI could add support using the -m flag to use PaLM 2 as an alternative to the default (gpt-3.5-turbo). The activation arguments coulld be -m palm-2.

Links

• https://blog.google/technology/ai/google-palm-2-ai-large-language-model/