Add 'Msty' as API Provider option

[armgitaar]

Add Msty as an option for API Provider.

Msty has similar setup as existing Ollama and LM Studio options - and selecting both today is a workaround.

For example, if you have Msty App or Msty Sidecar running, then you can select Ollama as API Provider and then retrieve Msty's local AI service endpoint and add it to base url, which then will pull into Roo Code the models that are running/available -

Msty docs:
App: https://docs.msty.app/
Studio/Sidecar: https://docs.msty.studio/