[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.

crates/ruff_db/src/files.rs

@@ -263,12 +263,23 @@ impl Files {
 
 impl fmt::Debug for Files {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        let mut map = f.debug_map();
+        if f.alternate() {
+            let mut map = f.debug_map();
 
-        for entry in self.inner.system_by_path.iter() {
-            map.entry(entry.key(), entry.value());
+            for entry in self.inner.system_by_path.iter() {
+                map.entry(entry.key(), entry.value());
+            }
+            map.finish()
+        } else {
+            f.debug_struct("Files")
+                .field("system_by_path", &self.inner.system_by_path.len())
+                .field(
+                    "system_virtual_by_path",
+                    &self.inner.system_virtual_by_path.len(),
+                )
+                .field("vendored_by_path", &self.inner.vendored_by_path.len())
+                .finish()
         }
-        map.finish()
     }
 }