Use datastore operator for postgres provisioning

[michaeljguarino]

This should be a more stable provisioning process overall

Test Plan

unit test

Checklist

• [ ] If required, I have updated the Plural documentation accordingly.
• [ ] I have added tests to cover my changes.
• [ ] I have added a meaningful title and summary to convey the impact of this PR to a user.
• [ ] I have added relevant labels to this PR to help with categorization for release notes.