SYS-687 ansible updates for Ubuntu 26.04

[instantlinux]

Summary of Changes

Ubuntu 26.04 came out. Here are the changes to support ansible playbooks here (k8s-node, fileserver and mythfrontend):

• docker and k8s versions bumped
• ssh-askpass added to k8s-node for use with git commit
• got rid of another case where ansible was still using apt_key and apt_repository (now ansible.builtin.deb822_repository)
• got rid of another case of deprecated gateway4 in netplan (now routes)
• replaced ntp with ntpd-rs

Why is this change being made?

The usual pile of deprecations broke several things. This brings the repo into more or less full compliance with Ubuntu's standards for this LTS release, to make dependency updates easier next couple of years.

How was this tested? How can the reviewer verify your testing?

Local testing

Completion checklist

• The pull request is linked to all related issues
• This change has unit test coverage
• Documentation has been updated
• Dependencies have been updated and verified