WIP: update equinix-metal usage examples

[displague]

Update Equinix Metal usage documentation and examples

I noticed some minor needs and this snowballed into recognizing that more of the Terraform examples would need to be updated.

I'm opening this as a draft to represent that need. Others should feel free to pick this branch up.

How to use

[ describe what reviewers need to do in order to validate this PR ]

Testing done

[Describe the testing you have done before submitting this PR. Please include both the commands you issued as well as the output you got.]

• Changelog entries added in the respective changelog/ directory (user-facing change, bug fix, security fix, update)
• Inspected CI output for image differences: /boot and /usr size, packages, list files for any missing binaries, kernel modules, config files, kernel modules, etc.

[tormath1]

Thanks a lot for updating this. I think we can go ahead and merge this and open an issue regarding https://github.com/flatcar/flatcar-terraform update?