Register tool functions of mcp servers again after restart of the frontend

[JonasHelming]

fixed #14701

What it does

• extract a frontend mcp service with the logic to start MCP servers and register their functions
• on Start of the frontend: register all functions of previously started mcp servers.

How to test

• Start a mcp server and use its functions
• Reload the frontend and check that the functions still work

Follow-ups

• Allow to auto-start mcp servers if the backend is restarted ([Theia AI] Allow to auto-start MCP servers on start-up #14692)

Breaking changes

• This PR introduces breaking changes and requires careful review. If yes, the breaking changes section in the changelog has been updated.

Attribution

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[sdirix]

Works for me!