add unit test and documentation for finalizers

[FxKu]

#941 added support for using finalizers. However, the PR lacked documentation and a unit test. We decided to merge it anyway due to the age of the PR in favor for having a quick follow-up PR which adds it.

The unit test became larger than anticipated:

• testing the whole Create() process of cluster.go
• All finalizer functions were turned private as they are not accessed from anywhere else in the code.
• Finalizers will not only added on Create and removed on Delerte but also managed sync
• The introduced JSON patch dependency was removed in favor for marshaling with Go like we do with the status
• The patch/update of Postgresql resource was moved to it's own function in k8sutil
• RemoveString function moved into util package and added unit test
• log messages starting with capital letter were lower cased

This PR also remove a binary debug file which was merged with #2456, unfortunately.

[jopadi]

👍

[FxKu]

👍