Add support for changing keystore parameters natively

[advxrsary]

Hello,

I have encountered an issue with setting up keystore in elasticsearch. I need to connect my aws s3 bucket as a repo for my snapshots, but for that I need to either grant permissions to the instance running SO, or provide access + secret keys via docker exec -it -u elasticsearch so-elasticsearch bin/elasticsearch-keystore add s3.client.aws-siem.access/secret_key.
Current setup resets all the keys after highstate.

So I am asking to provide support for configuring keys natively via so-elasticsearch-keystore command, as I can't use the first method.

[cm-ops]

This is something that is being looked at to add. I do not have a timeline for when however.