DBaaS: Replace all default passwords in operator secrets during installation

User story:

Right now, passwords  for cluster admin and monitoring are default passwords. We replace only password for PMM during operators installation. It's not secure to leave other passwords set to their default value.

Acceptance criteria:

User can replace all default passwords during installation.

How to test:

1. Check that new
2. Run `kubectl get secrets`
3. Find secrets related to newly created DB cluster.
4. Get passwords by running `kubectl get secrets  {secret-name}

   -o=yaml

1. Check that they different from each other, check that it generates new ones for each DB cluster.