SQL/MySQL: Add milliseconds in formatValue()

MySQL does understand ISO 8601 formatted datetime strings with
milliseconds so use Qt::ISODateWithMs instead Qt::ISODate within
formatValue().

Pick-to: 6.8 6.5
Task-number: QTBUG-95071
Fixes: QTBUG-136042
Change-Id: I182475c706c8eda0e3f97e23d98d3f91e372244a
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
(cherry picked from commit 5b6cbb9c4e)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/plugins/sqldrivers/mysql/qsql_mysql.cpp

@@ -1622,7 +1622,7 @@ QString QMYSQLDriver::formatValue(const QSqlField &field, bool trimStrings) cons
                 r = u'\'' +
                         dt.date().toString(Qt::ISODate) +
                         u'T' +
-                        dt.time().toString(Qt::ISODate) +
+                        dt.time().toString(Qt::ISODateWithMs) +
                         u'\'';
             }
             break;