…stic#82401)

resolves elastic#79785

Until now, the execution status was available in the the event
log document for the execute action.  In this PR we add it.

The event log is extended to add the following fields:

- `kibana.alerting.status` - from executionStatus.status
- `event.reason`           - from executionStatus.error.reason

The date from the executionStatus and start date in the event
log will be set to the same value.

Previously, errors encountered while trying to execute an
alert executor, eg decrypting the alert, would not end up
with an event doc generated.  Now they will.

In addition, there were a few places where events that could
have had the action group in them did not, and one where the
instance id was undefined - those were fixed up.