Always use `github.copilot.editingSessionEditor`, enable slash-command based on v2-config (#2060)

* Always use `github.copilot.editingSessionEditor`, enable slash-command based on v2-config

This makes all requests go to the `InlineChatIntent` and it decides (based on the v2-config) if it uses the "old world" for making inline chat requests happen

* re-run tests