Add healthcheck metric for IR

[vkarak1]

Could you please add a healthcheck metric for IR service?

Please the example of healthcheck metric for storage-node service:

root@az:/home/service# curl -s localhost:6672 | grep neofs_node_state_health | sed 1,2d
neofs_node_state_health 2

[fyrchik]

Do you have any specific use-case? What about control service Healthcheck?

[vkarak1]

It would be very helpful in failover test where kill/restart/hang for each service is issued and the test issues health check using _health metrics for most of the services, also this metric could be used for cluster monitoring.

[fyrchik]

frostfs-node and s3-gw have such metrics. Let's add a similar one to frostfs-ir.