add a way for an attempt to report an attempt failure

Currently AMs can report a failure with exit code and diagnostics text —but only when exiting to a failed state. If the AM terminates for any other reason there's no information held in the RM, just the logs somewhere —and we know they don't always last.

When an application explicitly terminates an attempt, it would be nice if it could optionally report something to the RM before it exited. The most recent set of these could then be included in Application Reports, so allowing client apps to count attempt failures and get exit details.