Document processes for out of support operating systems

This is a follow-on to the work in https://github.com/adoptium/infrastructure/issues/2902

In addition to the main machines in the jenkins CI, we have systems in various other places that we use as part of the infrastructure. This issue will cover making sure we have documentation on what to do when an operating system goes out of support, so we can remove it from the system entirely where feasible, and also to cover policies surrounding new releases (Both STS and LTS) of the platforms we use and ideally timescale targets.

Relevant previous issues:
- [AIX 7.1](https://github.com/adoptium/infrastructure/issues/3030)
- [Ubuntu 16.04 removal](https://github.com/adoptium/infrastructure/issues/1986)
- [Document https://github.com/adoptium/infrastructure/issues/2503

Places to consider:
- [ ] Jenkins / inventory (real machines)
- [ ] [DockerStatic containers](https://github.com/adoptium/infrastructure/tree/master/ansible/playbooks/AdoptOpenJDK_Unix_Playbook/roles/DockerStatic/Dockerfiles) used for test (See relevant [EPIC](https://github.com/adoptium/infrastructure/issues/3368))
- [ ] [VagrantPlaybookCheck](https://ci.adoptium.net/view/Tooling/job/VagrantPlaybookCheck/)/[QemuPlaybookCheck](https://ci.adoptium.net/view/Tooling/job/QEMUPlaybookCheck/)
- [ ] [DockerFileCheck](https://ci.adoptium.net/job/DockerfileCheck) (Is this still useful?)
- [ ] [Github actions](https://github.com/adoptium/infrastructure/tree/master/.github/workflows) (e.g. [this PR](https://github.com/adoptium/infrastructure/pull/3387))

Anything I've missed?

Start by reading the follow-on issue 2902 and the linked issues for AIX 7.1 and Ubuntu 16.04 removal. Review the Jenkins/inventory systems, DockerStatic Dockerfiles, VagrantPlaybookCheck, QemuPlaybookCheck, DockerFileCheck, and .github/workflows. Done means the out-of-support removal process and STS/LTS release policies are documented for each relevant location.

Written by the indexing model from the issue text.