Default Model Management

[JonasHelming]

PO @JonasHelming

Feature Description:

See eclipse-theia#15395

Minimal/First Iteration

• Chain of different default model aliases (code, universal, code completion, summarize)
• Model from chain is selected if an API key is available. Otherwise, try the next one in the chain. Default to first one if none has an API key
  • Users can override the chain for a default alias with a singular model (or also a chain if not more complicated)
  • Needs LanguageModel extension to see if a model is ready to use (i.e. has an API key)
    • Extend with status object property containing a status and an optional (error) message
• (default) model aliases are handled by a new service
• Add UI to see alias model chain and allow configuring a model. Probably add to AI configuration view.

[lucas-koehler]

Also see Theia upstream issue: eclipse-theia#15395

[lucas-koehler]

PR eclipse-theia#15782