RTGOV-160 Add interface to RPC activity type, and set value within the switchyard auditor
RTGOV-160 - interface now defined in the activity events and also used in service definitions as the key field. RTGOV-58 - serviceType is now purely used for the service implementation, which required restructing the service definition to have the interface/op definitions at the top level, but provide distinct element in case there are multiple service implementations supporting the same interface/op.