Overloading MunitSpy withAttributes(...) to accept org.mule.munit.common.mocking.Attribute object as a parameter to be consistent with MessageProcessorMocker withAttributes(…).

Overloading MunitSpy withAttributes(...) method to accept org.mule.munit.common.mocking.Attribute object as
a parameter as well as a Map to be consistent with
MessageProcessorMocker withAttributes(…).