MINOR: tevt: Add a sample to get termination events for all locations

MINOR: tevt: Add a sample to get termination events for all locations

"term_events" is a sample fetche function that can be used to get
termination events for all locations in one call. The format equivalent to:

  {fc_term_events,fc_mux_term_events,fs.term_events,txn.term_events,bs.term_events,bc_mux_term_events,bc_term_events}

If no event was reported for a location, the field is empty. If the feature
is not supported yet, a dash ('-') is printed.