Types: resolve services with Owner.lookup

Integrate the service registry into the `DIRegistry` introduced as part
of rationalizing the `Owner` types in PR #20271 (94276b5). This allows
`Owner.lookup('service:foo')` to resolve a `FooService` if one is set
up in the `@ember/service` module's `Registry` interface. The preview
types already used this mechanic, so this just means that when we ship
the stable (i.e. built from source) version of `@ember/service`, it
will *continue* working.

Meta: Shipping this implementation for the lookup was blocked on being
able to publish type modules with `declare module`, which was
implemented in PR #20316 (9adcd15). We will likely need to rework other
parts of the type hierarchy to support publishing from source.

packages/@ember/service/index.ts

@@ -93,3 +93,16 @@ export function service(
 export default class Service extends FrameworkObject {
   static isServiceFactory = true;
 }
+
+/**
+  A type registry for Ember `Service`s. Meant to be declaration-merged so string
+  lookups resolve to the correct type.
+ */
+// eslint-disable-next-line @typescript-eslint/no-empty-interface
+export interface Registry extends Record<string, Service> {}
+
+declare module '@ember/owner' {
+  export interface DIRegistry {
+    service: Registry;
+  }
+}