Expose context server settings to extensions (#20555)

This PR exposes context server settings to extensions.

Extensions can use `ContextServerSettings::for_project` to get the
context server settings for the current project.

The `experimental.context_servers` setting has been removed and replaced
with the `context_servers` setting (which is now an object instead of an
array).

Release Notes:

- N/A

---------

Co-authored-by: Max Brunsfeld <maxbrunsfeld@gmail.com>

Cargo.lock

@@ -2823,6 +2823,7 @@ dependencies = [
  "log",
  "parking_lot",
  "postage",
+ "project",
  "schemars",
  "serde",
  "serde_json",
@@ -4170,6 +4171,7 @@ dependencies = [
  "async-trait",
  "client",
  "collections",
+ "context_servers",
  "ctor",
  "env_logger 0.11.5",
  "extension",