test(language-service): Load language service from tsconfig (#30153)

This PR changes the integration test to load language service the way it would be loaded in the editor.
If the language service is specified in tsconfig, it'd only be loaded for Angular projects.
Specifying it as `globalPlugins` loads it unconditionally whenever tsserver is brought up.

PR Close #30153

integration/language_service_plugin/project/tsconfig.json

@@ -8,6 +8,9 @@
     "experimentalDecorators": true,
     "lib": [ "es2015", "dom" ],
     "noImplicitAny": true,
-    "suppressImplicitAnyIndexErrors": true
+    "suppressImplicitAnyIndexErrors": true,
+    "plugins": [
+      {"name": "@angular/language-service"}
+    ]
   }
 }

integration/language_service_plugin/test.ts

@@ -13,7 +13,6 @@ describe('Angular Language Service', () => {
   beforeEach(() => {
     jasmine.addMatchers(goldenMatcher);
     server = fork(SERVER_PATH, [
-      '--globalPlugins', '@angular/language-service',
       '--logVerbosity', 'verbose',
       '--logFile', join(PWD, 'tsserver.log'),
     ], {