feat: Add ACL related metrics

[dttung2905]

Hi team,

This PR aims to add more ACL related metrics for kminion, inititally brought up by #137. It will now support 2 different types of metrics

• Total number of ACLs
• Total number of ACLs broken down by different type

Below is an example output under /metrics endpoint

# HELP kminion_kafka_acls_by_type The number of ACLs by resource type
# TYPE kminion_kafka_acls_by_type gauge
kminion_kafka_acls_by_type{resource_type="cluster"} 1
kminion_kafka_acls_by_type{resource_type="group"} 2
kminion_kafka_acls_by_type{resource_type="topic"} 3
kminion_kafka_acls_by_type{resource_type="transactional_id"} 4
# HELP kminion_kafka_acls_total The total number of ACLs in the cluster
# TYPE kminion_kafka_acls_total gauge
kminion_kafka_acls_total 10

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[dttung2905]

Hi @weeco, could you help to take a look at this PR when you have time 🙏 ?

[dttung2905]

Hi @weeco just want to follow up whether there is anything that I need to do before we can merge this to upstream 🙏 ?