refactor: Update and migrate Video Block JS files into xmodule/assets

- Move Video Block JS files from xmodule/js/src/video/ to xmodule/assets/video/public/js/ 
- Update JavaScript files from  RequireJS to ES6 import/export
- test: Enable and fix Karma Js tests for Video XBlock (#37351)

---------

Co-authored-by: salmannawaz <salman.nawaz@arbisoft.com>

common/static/common/js/karma.common.conf.js

@@ -332,7 +332,11 @@ function getBaseConfig(config, useRequireJs) {
                 base: 'Firefox',
                 prefs: {
                     'app.update.auto': false,
-                    'app.update.enabled': false
+                    'app.update.enabled': false,
+                    'media.autoplay.default': 0, // allow autoplay
+                    'media.autoplay.blocking_policy': 0, // disable autoplay blocking
+                    'media.autoplay.allow-extension-background-pages': true,
+                    'media.autoplay.enabled.user-gestures-needed': false,
                 }
             },
             ChromeDocker: {