[ty] Request configuration from client (#18984)
## Summary
This PR makes the necessary changes to the server that it can request
configurations from the client using the `configuration` request.
This PR doesn't make use of the request yet. It only sets up the
foundation (mainly the coordination between client and server)
so that future PRs could pull specific settings.
I plan to use this for pulling the Python environment from the Python
extension.
Deno does something very similar to this.
## Test Plan
Tested that diagnostics are still shown.
