feat: Separated maintenance window setting for cluster and instances

[tomasbackman]

Description

Added separation of the maintenance window setting so that we can set different times for clusters and instances. Since that is possible to do in the aws GUI.

[tomasbackman]

@antonbabenko should I just put you as reviewer or is there anyone else in this project that can review and merge pull requests? )Since you are marked as busy

[geototti21]

Should we add also an option to define different maintenance windows for each instance, I assume we don't want the instances to have exactly the same maintenance window in case we do type upgrades, etc.. (and we don't apply the upgrades immediately from the console) ?

[tomasbackman]

Should we add also an option to define different maintenance windows for each instance, I assume we don't want the instances to have exactly the same maintenance window in case we do type upgrades, etc.. (and we don't apply the upgrades immediately from the console) ?

Yes, fixing

[github-actions]

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