Removal of QByteArray methods taking QByteArray (in favour of QByteArrayView) is a SIC

In Qt 6 in QByteArray we've ditched a bunch of overloads taking QByteArray, leaving only the ones taking QByteArrayView instead

https://codereview.qt-project.org/c/qt/qtbase/+/303768

This change is, well, SIC compared to Qt 5: we can no longer pass to those functions datatypes that convert to QByteArray (and not QByteArrayView).

We've got a pretty big offender in Qt itself: QStringBuilder. This code works in Qt 5 and doesn't in Qt 6:

QByteArray a, b, haystack;
haystack.contains(a % b);

Possible solutions:

1. re-introduce the overloads taking QByteArray (with the usual shenanigans to avoid ambiguities )
2. make QStringBuilder convertible not just to the "storage" class but to the respective view class as well (risks dangling, but it's OK in the use-case above. One can always dangle with views QStringView v = str1 + str2, with or without QStringBuilder being used)
3. make QByteArrayView buildable from any type convertible to QByteArray, incl. QStringBuilder. This is employed by QAnyStringView.