Footer action menu with `extra_footer_actions` needs better styling

[Dan Braghiș]

We switched to using Tippy for the action menu in #11456

While we don't necessarily describe how the action bar behaves when extra_footer_actions is in use, it currently breaks.

See torchbox/wagtail-content-import#60 (putting aside the fact it is using the old <li> format), and the following screnshot from wagtail-localize (I am currently working on the Wagtail 6.0 compatibility for it)

[LB (Ben Johnston)]

I have been able to reproduce this as follows;

Create a new template to override the Page Create template (e.g. .../templates/wagtailadmin/pages/create.html) & then create a page.

{% extends "wagtailadmin/pages/create.html" %}

{% block extra_footer_actions %}
  <a href="#none" class="button">Link</a>
  <button class="button" type="button">Button</button>
{% endblock %}

it appears that the clean up done with #11629 removed a bit of base styling that should reasonably be relied upon in my opinion.

[LB (Ben Johnston)]

PR up with a proposed fix #11751