[Enhancement] Add Key expiration alerting and monitoring

[peterzhuamazon]

The key management of our releases needs to be monitored.

1. The general key for all the signatures on artifacts
2. The key specifically for the ruby artifacts like opensearch-ruby and logstash-oss-opensearch.

They will expire in about a year:

1. Need to extend 20230512 [Renew Key] Upcoming expiration of our current sub public key (expire on 20230512)  #2136
2. Need to extend / recreate 20220802

Acceptance criteria

• Monitor the current status along with the expiration is added for all the keys used for signing the OpenSearch artifacts (including clients and standalone components)
• Automated alerting mechanism is in place for all the keys used for signing the artifacts
• Create dashboards to view the current status of all the keys

[rishabh6788]

The signing key metrics are now getting published for our internal monitoring.