also str representation of unicode character is different.

See merge request !1754

This fixes some regressions introduced by !1545 when searching the catalog for non ascii text

See merge request !1752

Using unicode with a catalog key or related key got broken in the merge
of zope4 support, but using unicode on a translated key (such as
translated_portal_type or translated_validation_state_title) was not
working before.

it supports text, but unless they have non-ASCI characters, so it's
better to always pass bytes.

In original Products.ZSQLMethods, this is text, we want to keep the
same semantics and encode only at a lower level.

MySQLdb's string_literal is a method from the C API and the name is not
natural for python programmers, because it manipulates bytes. It
supports str, unless they have non ASCII characters, so it's better to
always pass bytes.

On python2, this change repairs a regression visible when searching
catalog with translated related keys. This regression was introduced in
the merge of zope4 support, more specifically with 610972af (py3:
Update Shared.DC.ZRDB.{sqltest,sqlvar} monkey patches., 2022-04-16),
because with the new version of the patches this method gets passed
unicode strings, which is fine, unless they contain non ASCII characters.