feat(language-service): add definitions for styleUrls (#32464)

Adds support for `styleUrls` definitions in the same way `templateUrl`
definitions are provided; clicking on styleUrl will take a user to the
respective file.

Unifies some code in determining a URL definition. We first check if a
url is a `templateUrl`; if it's not, we check that it's a `styleUrl` or
return no definitions.

PR Close #32464

packages/language-service/test/definitions_spec.ts

@@ -275,4 +275,27 @@ describe('definitions', () => {
     expect(def.fileName).toBe('/app/test.ng');
     expect(def.textSpan).toEqual({start: 0, length: 0});
   });
+
+  it('should be able to find a stylesheet from a url', () => {
+    const fileName = mockHost.addCode(`
+	      @Component({
+	        templateUrl: './test.ng',
+                styleUrls: ['./«test».css'],
+	      })
+	      export class MyComponent {}`);
+
+    const marker = mockHost.getReferenceMarkerFor(fileName, 'test');
+    const result = ngService.getDefinitionAt(fileName, marker.start);
+
+    expect(result).toBeDefined();
+    const {textSpan, definitions} = result !;
+
+    expect(textSpan).toEqual({start: marker.start - 2, length: 10});
+
+    expect(definitions).toBeDefined();
+    expect(definitions !.length).toBe(1);
+    const [def] = definitions !;
+    expect(def.fileName).toBe('/app/test.css');
+    expect(def.textSpan).toEqual({start: 0, length: 0});
+  });
 });