Port the string-based singleShot() static methods from milliseconds to nanoseconds resolution. This matches what QChronoTimer provides, but we want to minimize porting for users come Qt 7, so we don't want users to first have to port to QChronoTimer::singleShot() and then back to QTimer::singleShot(); we want them to continue to use QTimer. The only reason QChronoTimer is a separate class from QTimer is that the latter has an int interval property and we can't just port it to milli- or nanoseconds chrono types if we want users to actually access the extra range or precision afforded by the chrono types. But that's not an issue for the singleShot() static methods, as they never return an object that could be asked for its timeout. The new-style static methods will be ported in a second step. [ChangeLog][QtCore][QTimer] The singleShot() static methods now operate with nanoseconds resolution, like QChronoTimer. The rest of QTimer remains milliseconds; use QChronoTimer if you need a QTimer with nanoseconds resolution of more than INT_MAX milliseconds range. Beware overflow that may occur when passing large milliseconds objects that may overflow nanoseconds::rep when converted. Pick-to: 6.8 Task-number: QTBUG-128426 Change-Id: I11e1ad8529c67b4018f6325ac408686799475823 Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>