Add a vmware-k8s-1.20 variant

[zmrow]

Issue number:
Closes #1451

Description of changes:
This change adds the necessary files for a VMware Kubernetes 1.20 variant.

This variant is currently able to join Kubernetes clusters on VMware given the proper user data.

Testing done:
All nodes used the following user data:

[settings.kubernetes]
api-server = "<redacted>"
cluster-dns-ip = "<redacted>"
bootstrap-token = "<redacted>"
cluster-certificate = "abc123"

[settings.host-containers.admin]
enabled=true
user-data = "<redacted>"

[settings.host-containers.control]
enabled = true
user-data= "<redacted>"

Built a vmware-k8s-1.20 OVA and uploaded to vSphere. Booted 3 nodes using the above user-data via guestinfo.userdata. The nodes boot and properly join a previously provisioned CAPV cluster.

• Ensure that vmtoolsd is running and green
• All taints are removed and hosts are schedulable. All cluster pods running successfully on the nodes (calico, vsphere-csi, etc)
• Run a busybox pod
• Inspected journal logs; nothing alarming there
• Host containers work normally
  • SSH to the node's IP address to ensure that admin container works. sudo sheltie works as normal
  • Use SSM to start a session on the control container. Everything works as normal
• Sonobuoy testing passed.

Plugin: e2e
Status: passed
Total: 5667
Passed: 309
Failed: 0
Skipped: 5358

Plugin: systemd-logs
Status: passed
Total: 4
Passed: 4
Failed: 0
Skipped: 0

Terms of contribution:

By submitting this pull request, I agree that this contribution is dual-licensed under the terms of both the Apache License, version 2.0, and the MIT license.

[zmrow]

^ Fix the Cargo.lock... oops :)

[zmrow]

• Rebased on develop (sorry this rebase should have been in a different push to make the diff easier to read)
• Added supported_arches and kernel-parameters
• Removed static-pods

[webern]

🍰

[zmrow]

Updated to use K8s 1.20 and integrated all the requested feedback.

#1510 is being worked by @bcressey separately and will have a separate PR to merge into this variant.

Marked this PR as ready for review.

[tjkirch]

I'm working on the config refactors for #1511 (comment) and #1511 (comment).

[zmrow]

^ Addresses @tjkirch 's comments

[zmrow]

^ rebase on develop, no changes.

[zmrow]

^ Adds the kernel to Cargo.toml and updates Cargo.lock

[tjkirch]

^ Wow, sorry. I thought I was being funny by saying my PR would resolve a comment in this PR, but it closed the whole PR. Reopened!

[zmrow]

^ rebase on develop, no changes (yet)

[zmrow]

^ Yet another rebase on develop, no changes (yet)

[zmrow]

^ Addressed all the changes necessary after rebase and addressed remaining PR comments!