Add support to use other LLM platforms

[StashaS]

Context: Current implementation supports only GCP, which is not fair for other vendors. :)

Task:

1. Split the tooklit logic to actual toolkit and client to request LLM model provider.
2. Move clients LLM provider logic to separate packages.
3. Add support and instructions for the popular LLM platforms.

Result: User should be able to configure and choose LLM platform.