Get monitors state in metrics (prometheus) format for authorized user.

Example of success response:

# HELP `healthcheck_state` The `healthcheck_state` metric reflects the state of a specific monitor after conducting a health check
# TYPE `healthcheck_state` gauge
`healthcheck_state`{`client_id`="1",`monitor_id`="431",`monitor_locations`="us-east-1,us-west-1",`monitor_name`="test-monitor-1",`monitor_type`="http",`rrset_name`="rrset-name1",`rrset_type`="rrset-type1",`zone_name`="zone-name1"} 0
`healthcheck_state`{`client_id`="1",`monitor_id`="4871",`monitor_locations`="fr-1,fr-2",`monitor_name`="test-monitor-2",`monitor_type`="tcp",`rrset_name`="rrset-name2",`rrset_type`="rrset-type2",`zone_name`="zone-name2"} 1
`healthcheck_state`{`client_id`="2",`monitor_id`="7123",`monitor_locations`="ua-1,ua-2",`monitor_name`="test-monitor-3",`monitor_type`="icmp",`rrset_name`="rrset-name3",`rrset_type`="rrset-type3",`zone_name`="zone-name3"} 0