[WIP][ticket/12853] Change navbar ACP from skip- to last-responsive

One small problem with this is that we recently moved the ACP/MCP to the end of the list (in order to prevent the links from jumping when MCP is not available on certain pages). See: https://tracker.phpbb.com/browse/PHPBB3-12824

So when we change ACP to responsive-last, it will be handled like other links, and placed in the dropdown in the same order. The result will be that it will be placed between FAQ and the other quick-links.

I don't suppose we want this.

If this is indeed unacceptable, we basically have 2 options. [1] Move the ACP back to the front of the list, or [2] use JS to detect the ACP and move it to the top of the list.

https://tracker.phpbb.com/browse/PHPBB3-12853
PHPBB3-12853