MULE-7703: Add a way to configure default threading profile

_Adding system properties to configure default values.
_Adding test for default values
_NOTE: there are no test checking for custom values as I found no way to do it without doing using reflection
I think it makes more sense to use defaultThreadingProfile.  In configuration we use the "default" prefix to, to make it clear this is default not single threadingProfile used across Mule.