refactor: move xmodule folder to root

- Moving xmodule folder to root as we're dissolving sub-projects of common folder in edx-platform
    - More info: https://openedx.atlassian.net/browse/BOM-2579
- -e common/lib/xmodule has been removed from the requirements as xmodule has itself become the part of edx-platform and not being installed through requirements
- The test files common/lib/xmodule/test_files/ have been removed as they are not being used anymore

cms/static/cms/js/require-config.js

@@ -123,7 +123,7 @@
             'backbone.paginator': 'common/js/vendor/backbone.paginator',
             'tinymce': 'js/vendor/tinymce/js/tinymce/tinymce.full.min',
             'jquery.tinymce': 'js/vendor/tinymce/js/tinymce/jquery.tinymce.min',
-            'xmodule': '/xmodule/xmodule',
+            'xmodule': '/xmodule',
             'xblock/cms.runtime.v1': 'cms/js/xblock/cms.runtime.v1',
             'xblock': 'common/js/xblock',
             'utility': 'js/src/utility',

cms/static/xmodule_js

@@ -1 +1 @@
-../../common/lib/xmodule/xmodule/js/
+../../xmodule/js