fingerprint: add fingerprinting for CNI plugin versions

[shoenig]

This PR adds a fingerprinter to set the attribute
"plugins.cni.version.<name>" -> version of the CNI plugin if present at $client.cni_path

First half of #14022
Second half will be adding an implicit constraint on applicable jobs.

e.g.

➜ nomad node status -self -verbose | grep plugins.cni.version
plugins.cni.version.bandwidth   = v1.0.0
plugins.cni.version.bridge      = v1.0.0
plugins.cni.version.custom      = v1.0.3
plugins.cni.version.dhcp        = v1.0.0
plugins.cni.version.firewall    = v1.0.0
plugins.cni.version.host-device = v1.0.0
plugins.cni.version.host-local  = v1.0.0
plugins.cni.version.ipvlan      = v1.0.0
plugins.cni.version.loopback    = v1.0.0
plugins.cni.version.macvlan     = v1.0.0
plugins.cni.version.portmap     = v1.0.0
plugins.cni.version.ptp         = v1.0.0
plugins.cni.version.sbr         = v1.0.0
plugins.cni.version.static      = v1.0.0
plugins.cni.version.tuning      = v1.0.0
plugins.cni.version.vlan        = v1.0.0
plugins.cni.version.vrf         = v1.0.0

Targets 1.5.0

[shoenig]

Spot check

➜ nomad node status -self -verbose | grep plugins\.cni
plugins.cni.version       = v1.0.0

[lgfa29]

Minor comments, but no blockers. Good one!

The v stuff in the fingerprint may be worth checking just to make sure it works with constraint and affinity.

[shoenig]

Backporting this so that #14022 can be merged sooner than later; the implicit constraint cannot be injected until users are already on a version of Nomad that fingerprints the CNI plugin.

[github-actions]

I'm going to lock this pull request because it has been closed for 120 days ⏳. This helps our maintainers find and focus on the active contributions.
If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.