QIODevice::readLineInto() should have a QSpan overload

QIODevice now has readLineInto(QByteArray *, qint64), but that is still dependent on a QByteArray and therefore needs at least one (initial) allocation.

In many cases, a static or automatic buffer would be sufficient, such as a C array or a QVLA. For these callers, we should also have an overload of the QCryptographicHash::hashInto form:

QByteArrayView QIODevice::readLineInto(QSpan<std::bytes> buffer); // + char and uchar overloads delegating to this

cf. https://doc-snapshots.qt.io/qt6-dev/qcryptographichash.html#hashInto-3

Doesn't need the maxSize parameter, as that would be the same as buffer.size().

Could even have readInto() (non-Line) in the same style.