bug: support instance class when restoring a db cluster from a snapshot

[dillen-roggensinger]

Description

The db_cluster_instance_class property was not respected when restoring a cluster from a snapshot despite the API supporting it.

Relations

Closes #26773

References

RestoreDBClusterFromSnapshot documentation containing DBClusterInstanceClass.

[github-actions]

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[github-actions]

Welcome @dillen-roggensinger 👋

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