Get rid of global _apiUtil

* Replace the global _apiUtil variable with named functions imports.
* Update gr-app-global-var-init.js

Change-Id: I3e897db0f4611d2abcb68d0431e145f21530bc9b

polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-api-utils_test.html

diff --git a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-api-utils_test.html b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-api-utils_test.html
index 9586ccb..13e3a06 100644
--- a/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-api-utils_test.html
+++ b/polygerrit-ui/app/elements/shared/gr-js-api-interface/gr-api-utils_test.html
@@ -27,12 +27,12 @@
 <script type="module">
 import '../../../test/common-test-setup.js';
 import './gr-js-api-interface.js';
+import {getPluginNameFromUrl} from './gr-api-utils.js';
+
 const PRELOADED_PROTOCOL = 'preloaded:';
 
 suite('gr-api-utils tests', () => {
   suite('test getPluginNameFromUrl', () => {
-    const {getPluginNameFromUrl} = window._apiUtils;
-
     test('with empty string', () => {
       assert.equal(getPluginNameFromUrl(''), null);
     });