feat: add llm-host to manage llm worker provider/client + llm config

[grjte]

This creates a new llm-host package that actually instruments the new patchwork-worker architecture for the llm case. It creates plugins for the patchwork:worker of kind llm (which uses the patchwork-llm library) and patchwork:worker-client of kind llm. It also adds llm config handling, moved out from the chat tool to here.

[patchcrow]

🪡 Patchwork preview

Torn down.