Revert "Reimplement qBinaryFind in terms of std::lower_bound"

After a bit of discussion, we should actually deprecate qBinaryFind too.
This puts the old code back (to avoid behavior changes / source
breaks).

This reverts commit 23d7f6ee5dea3dd9f47f4ab538b25dc0ffe3df92.

Task-number: QTBUG-33473

Change-Id: I7f7d25171e14061e51543c501c30a7b6b184a8fd
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>