Agent Instrumentation fails silently if method descriptors don't match

Currently if the agent is given an xml file with a valid method/class name but an incorrect descriptor (while still being valid for parsing purposes), the agent will proceed with instrumentation, creating and injecting the event classes but they will never be emitted. We should at least give a warning that the method descriptor is incorrect rather than failing silently and proceeding.

Reproducer:

probe.xml

Reproducer.java