Track stale service checks

[wbollock]

It should be possible to track stale service checks with the data under the objects/servicestatus endpoint. Between

             "current_state": "0",
            "has_been_checked": "1",
            "should_be_scheduled": "1",
            "current_check_attempt": "1",
            "max_check_attempts": "4",
            "last_check": "2020-04-06 14:16:30",
            "next_check": "2020-04-06 14:21:30",
            "check_type": "0",
            "check_options": "0",
            "last_state_change": "2020-02-01 16:10:38",
            "last_hard_state_change": "2020-02-01 16:10:38",
            "last_hard_state": "0",
            "last_time_ok": "2020-04-06 14:16:30",

these options, it's probably possible to determine if a service (and host?) check is stale.