inventory: Add specs for macstadium systems for reference

[sxa]

Updates to record the specs of the macstadium machines pending a review of what we're using at this provider.
Noting that the larger test-macstadium-macos1014-x64-4 was listed as a build- prefixed machine in the macstadium UI but I've now renamed it, although it does not seem to have been contactable for a while.

Checklist

• commit message has one of the standard prefixes
• faq.md updated if appropriate
• other documentation is changed or added (if applicable)
• playbook changes run through VPC or QPC (if you have access)
• VPC/QPC not applicable for this PR
• for inventory.yml changes, bastillion/nagios/jenkins updated accordingly