Document steps to set up a new etcd arm64 github runner

[jmhbnz]

What would you like to be added?

This is a sub issue under #15951.

The etcd project currently has two arm64 c3.large.arm machines generously contributed by Equinix Metal through the CNCF Community Infrastructure Lab. These machines are used to run our etcd arm64 ci infrastructure.

Situations can emerge where the project could be required to provision new machines, for example adding more capacity or changes to underlying operating system choice or hardware types.

We currently don’t have any project documentation that steps through the process we need to follow to set up newly created machines so that they would be ready to accept arm64 ci jobs for the etcd project.

This task will require someone with access to the existing machines to review the bash history of the root and runner users and then transpose the key steps into documentation, script or playbook form for easy use in future. Ideally these steps should then be tested on a new machine to verify they work as expected.

We should carefully review upstream existing documentation for github runners and ensure we link and reuse as much as possible: https://docs.github.com/en/actions/hosting-your-own-runners/managing-self-hosted-runners/about-self-hosted-runners

The documentation should be created under our newly created “infrastructure-guide” docs directory https://github.com/etcd-io/etcd/tree/main/Documentation/infrastructure-guide.

Why is this needed?

To have confidence in our arm64 ci infrastructure so we can proceed with tier 1 support.