agent: Improve the UX around interacting with MCP servers (#32622)

Still a work in progress! Todos before merging:

- [x] Allow to delete (not just turn off) an MCP server from the panel's
settings view
- [x] Also uninstall the extension upon deleting the server (check if
the extension just provides MCPs)
- [x] Resolve repository URL again
- [x] Add a button to open the configuration modal from the panel's
settings view
- [x] Improve modal UX to install and configure a non-extension MCP

Release Notes:

- N/A

---------

Co-authored-by: Bennet Bo Fenner <bennetbo@gmx.de>
Co-authored-by: Ben Brandt <benjamin.j.brandt@gmail.com>

Cargo.lock

@@ -71,6 +71,7 @@ dependencies = [
  "db",
  "editor",
  "extension",
+ "extension_host",
  "feature_flags",
  "file_icons",
  "fs",
@@ -127,7 +128,6 @@ dependencies = [
  "time",
  "time_format",
  "ui",
- "ui_input",
  "urlencoding",
  "util",
  "uuid",