[ActiveContext Code] Add button to disable semantic code search

Add a way for admins to disable semantic code indexing for an instance.

Clicking the button should:

• Stop indexing (TBD how that would work), maybe delete the connection is the best way
• Delete the partitions
• Deleting the connection will delete all enabled namespaces which will trigger repositories to be deleted which also deletes the data from the indices (but they would be deleted by this point)