fix: Prevent mocha tests failures when window does not have focus. (#9332)

* chore: Add puppeteer-core as a dev dependency.

* fix: Make mocha tests run in a fake-focused window.

* fix: Make `test:mocha:interactive` use the same gulp codepath as `test`.

gulpfile.mjs

@@ -45,7 +45,11 @@ import {
   publishBeta,
   recompile,
 } from './scripts/gulpfiles/release_tasks.mjs';
-import {generators, test} from './scripts/gulpfiles/test_tasks.mjs';
+import {
+  generators,
+  interactiveMocha,
+  test,
+} from './scripts/gulpfiles/test_tasks.mjs';
 
 const clean = parallel(cleanBuildDir, cleanReleaseDir);
 
@@ -80,6 +84,7 @@ export {
   clean,
   test,
   generators as testGenerators,
+  interactiveMocha,
   buildAdvancedCompilationTest,
   createRC as gitCreateRC,
   docs,