Move dom related utils from `scripts/util.js` to `utils/dom-util.js`

Also replace existing usages and add more tests on all util methods.

Change-Id: I89e0d9413153bfc115cd989ca7c66893b9709cc2
diff --git a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view_test.js b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view_test.js
index 1362fe3..faa81b6 100644
--- a/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view_test.js
+++ b/polygerrit-ui/app/elements/change/gr-change-view/gr-change-view_test.js
@@ -24,7 +24,7 @@
 import {KeyboardShortcutBinder} from '../../../behaviors/keyboard-shortcut-behavior/keyboard-shortcut-behavior.js';
 import {GrEditConstants} from '../../edit/gr-edit-constants.js';
 import {_testOnly_resetEndpoints} from '../../shared/gr-js-api-interface/gr-plugin-endpoints.js';
-import {util} from '../../../scripts/util.js';
+import {getComputedStyleValue} from '../../../utils/dom-util.js';
 import {GerritNav} from '../../core/gr-navigation/gr-navigation.js';
 import {pluginLoader} from '../../shared/gr-js-api-interface/gr-plugin-loader.js';
 import {_testOnly_initGerritPluginApi} from '../../shared/gr-js-api-interface/gr-gerrit.js';
@@ -320,7 +320,7 @@
   });
 
   const getCustomCssValue =
-      cssParam => util.getComputedStyleValue(cssParam, element);
+      cssParam => getComputedStyleValue(cssParam, element);
 
   test('_handleMessageAnchorTap', () => {
     element._changeNum = '1';