[Epic] Validate newer external database versions

[rancher-max]

Is your feature request related to a problem? Please describe.
Our current list of databases, per https://docs.k3s.io/datastore, are becoming stale again and the latest versions should be validated and documented. This is a followup to the previous work done a year ago in #5859.

Describe the solution you'd like
We need to validate K3s against newer versions of these databases:

• MariaDB 10.11
• PostgreSQL 15.3

In addition, we should drop support for some of the older versions of DBs that we have that are EOL. These include:

• PostgreSQL 10.7

[rancher-max]

@VestigeJ for Postgre validations

[VestigeJ]

Postgresql 15.5 validated
v1.25
v1.26
v1.27
v1.28