Add better TRACE-level debugging for EJBClientInvocationContext state machine

[rachmatowicz]

This is a draft pull request to add better trace level logging to EJBCientInvocationContext state machine.

[rachmatowicz]

The idea was to do two things:

• add in DEBUG level lohgging on more of the methods which were not getting visiility, like cancellation, discarding, failing, result ready,...
• for all state machine methods, add TRACE level debugging on most of the state transactions and conditions

This may require a bit of tweaking to get the balance right. We should probably also use the Logs.INVOCATION logger for the trace level messages as well (i.e. not log.tracef() but Logs.INVOCATION.tracef())

[tadamski]

@rachmatowicz I would go on and merge this branch and we can fine-tune later if necessary wdyt?