feat(core): add CLI commands to render / exec prompts

[mhordynski]

Feature description

Ragbits cli should provide a handy way to render / execute given prompt via CLI.

ragbits prompts render my_app.module.prompts:QAPrompt --payload={"question": "my question"}

ragbits prompts exec my_app.module.prompts:QAPrompt --payload={"question": "my question"}

Motivation

Prompt management is core feature of ragbits, it should be supported in CLI for developer experience.

Additional context

No response