This version of arg(), unlike its QString counterpart, transparently accepts
views without conversion to QString, and is also extensible to further argument
types, say a future QFormattedNumber.
[ChangeLog][QtCore][QStringView/QLatin1String] Added arg(), taking arbitrarily
many strings.
Change-Id: If40ef3c445f63383e32573f3f515fdda84c7fe3a
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>