[ChangeLog][QtCore][QString/QByteArray] Added slice() methods that work
like sliced(), but modify the string/byte-array they are called on.
Task-number: QTBUG-99218
Change-Id: I3075562983ef123d9aa022a2304c7e774cf2ea42
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>