QSqlQueryModel::setQuery() don't use deprecated reset()

QSqlQueryModel::setQuery() don't use deprecated reset()

Previously the method attempted to reset only as a last resort.

Now reset() is deprecated and resetting must happen between emitting
modelAboutToBeReset() and modelReset(). Since this suffices in all
cases to notify views that they must reinterrogate the model, it is no
longer necessary to signal explicitly row removals and insertions
within the scope of the reset.

Additionally, fetchMore() is now called within the scope of the reset
so insert signals do not have to be emitted here either.

This improved handling of resetting in QSqlQueryModel also allows the
cache in QSqlTableModel to be cleared directly at select().

This change may actually allow views to operate more efficiently since
they no longer have to react to separate row removal and insert
signals. Views can avoid pointless deallocation and reallocation
by considering row count only after the reset is finished. The cost is
that the columns and horizontal headers must be considered in the view
at each setQuery() call. In any case, it is not clear that trying to
be smart about this in the model justifies additional complexity.

Tests had to be adjusted where they expected explicit row removal
and insert signals.

Change-Id: I4f7eac1419824361d7d9bdcc6a87092b33e80d7a
Task-Id: QTBUG-25419
Reviewed-by: Andy Shaw <andy.shaw@digia.com>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Honglei Zhang <honglei.zhang@nokia.com>