Support PostgreSQL 16

[ianballou]

PostgreSQL 13 is blocking Foreman in numerous ways:

• EL10 support
• Django 5 support (Pulp & Katello)
• Red Hat Lightspeed integration

foremanctl needs to automate the migration to PG16, fresh installation of it, and test its compatibility with our existing tools.

[ekohl]

We already test on EL10:

foremanctl/.github/workflows/test.yml

Line 51 in 4e40a7e

- centos/stream10

However, you are right that we deploy a PostgreSQL 13 container:

foremanctl/src/vars/images.yml

Lines 17 to 18 in 4e40a7e

	postgresql_container_image: quay.io/sclorg/postgresql-13-c9s
	postgresql_container_tag: "latest"

[evgeni]

#395 has some test around the fresh install part of this.