[FEATURE] Operator should automatically update User password if it was changed in the Secret

[evheniyt]

Right now, it is impossible to update a User password if it was changed in the corresponding Secret.

Operator already has a handleSecretEvent functionality, but in the current implementation, it is useless. Yes, it will trigger reconcile if smth was changed in the Secret, but because of the logic inside Users Reconcile function it will do nothing if password was updated.

The main problem is that Opensearch API is not returning a User password so you couldn't just compare it like Operator does with other properties.

Proposal: Operator should automatically update User password if it was changed in the Secret.

[evheniyt]

@swoehrl-mw I have few ideas on how we could improve and implement this, would you like me to share a PR?