Remove hardcoding of language switcher in Mega Menu

Summary

The current implementation of the mega menu has the language switcher block hardcoded in the template:

              <ul class="dropdown-menu">
                <li>{{ drupal_block('language_block:language_interface') }}</li>
              </ul>

The issue is that it always render whether the user wants it or not.

Implementation

• Remove the hardcoding of the language switcher so that it will not render all the time.
• The language switcher should render like in the normal CERN theme by placing it in the block layout ** under the mega menu ** block.
• Make sure that the LS renders inline with the mega menu