This template function streams the given object into a QDebug instance
that operates on a string, and then returns that string.
This function is useful for cases where you need the textual
representation of an object for debugging, but cannot use operator<<.
A good example of this is when writing tests where you want to provide
a useful failure message involving details about an object, but must
provide it in a string to e.g. QVERIFY2.
[ChangeLog][QtCore][QDebug] Added static template toString() function,
which streams the given object into a QDebug instance that operates on
a string, and then returns that string.
Fixes: QTBUG-82309
Change-Id: I8411394e899dedad19cec788d779a4515d52ba11
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
658b9697f9