Add executionsSucceeded to supported SF alarms metrics

# This is a Feature Proposal

## Description

For feature proposals:
   For the allowable cloudwatch alarms, can we add `executionsSucceeded`, I'd like to be notified when a flow succeeds
* If there is additional config how would it look
      alarms:
        topics:
          ok: {}
          alarm: {}
        metrics:
          - executionsSucceeded