This reverts commit 5d13215b58f93c6be8255ef2e3e20836508c7d47.

``searchfield.html`` is similar to the existing ``searchbox.html``, but does not
have the heading "Quick Search". Instead, it uses "Search" as a placeholder
text. This gives a cleaner and less cluttered appearance.

The searchfield component is added to the basic theme and thus can be used
in any derivative theme. It is not used by default for backward compatibility.

The searchfield compenent is made the default in the sphinx13 theme.

CSS changes ensure that the top of the search field is aligned with the
top of the main content.

Add link to Weblate in intl documentation

Previous commit applied longtable class to the next one, but this still
left the previous table prevent an earlier page break.

Now that #11268 has been fixed via #11319.

Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>

Fix several reference errors throughout the documentation and set
``nitpick_ignore`` in ``doc/conf.py``.