[Direct To 5.15] add InitCotnainers to DB sts if not exist

[dannyzaken]

Explain the changes

• this change is done directly on 5.15. The code in the master (5.16 and up) removes the need for an init container.

• upgrade of postgres 12 to 15 assumes there is an init container to the DB sts.

• in some cases, it is possible that the DB is running without an init container.

• If no init container exists, the operator will crash when attempting to access the init containers array.

• The fix adds an init container to the pod spec from the DB statefulset template (statefulset-postgres-db.yaml)

Issues: Fixed #xxx / Gap #xxx

1. Fixes https://bugzilla.redhat.com/show_bug.cgi?id=2281839

Testing Instructions:

1. install noobaa
2. stop the operator
3. remove the init container from DB sts
4. start the operator. it should now add the init container back.

• [ ] Doc added/updated
• [ ] Tests added