Automate some Server labels

[Ulexus]

As part of the process following the #282 LabelSelector feature, we should automatically add some well-known labels to make things easier.

Examples (not final, just ideas):

• sidero.dev/cpu-architecture = amd64
• sidero.dev/cpu-core-count = 8
• sidero.dev/disk-count = 4
• sidero.dev/disk-count-nvme = `2'
• sidero.dev/disk-count-ssd = 2
• sidero.dev/network-interface-count = 4
• sidero.dev/network-interface-count-1g = 2
• sidero.dev/network-interface-count-10g = 2

The current system information is mostly opaque, uparsed string data, which is difficult to make use of, in terms of ServerClasses. Offering some well-known labels will help make ServerClass construction easier. We should, however, balance the number of labels automatically added with their utility.

[andrewrynhard]

To start, I wonder if what iPXE/PXE provides makes sense as a starting point:

2021/05/22 00:10:21 HTTP GET /ipxe?uuid=15839a00-8f07-11e9-8000-ac1f6bf200c2&mac=ac-1f-6b-f2-00-c2&domain=&hostname=&serial=S329106X9705490&arch=x86_64

[Ulexus]

The only one of these which jumps out at me the is arch, but Kubernetes already handles that. I don't think UUID, MAC, hostname, or serial number make sense as labels (indexed selectors) as opposed to general data in the spec.