Use int32 for PostgresVersion in Go structs

[cbandy]

This aligns the PostgresCluster and PGUpgrade structs. Tidy up some Job YAML, too.

Checklist:

• Have you added an explanation of what your changes do and why you'd like them to be included?
• Have you updated or added documentation for the change, as applicable?
• Have you tested your changes on all related environments with successful results, as applicable?
  • Have you added automated tests?

Type of Changes:

• Other

Other Information:

These formats in CRDs kinda do something but also not: https://issue.k8s.io/133880#issuecomment-3257062147