unixPB: RISC-V updates and use docker.io on Ubuntu 20+

[sxa]

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) https://ci.adoptium.net/view/Tooling/job/VagrantPlaybookCheck/1670/
• for inventory.yml changes, bastillion/nagios/jenkins updated accordingly

Likely supercedes #2850 as this has extra changes and makes the docker.io install not specific to RISC-V

This will allow us to easily set up the rest of the PLCTlab machines as per #3078

[sxa]

Merged into a larger PR at https://github.com/adoptium/infrastructure/pull/3240/files#diff-16ce648b78d7b0287c80fd49e23ba14f9bf18c1a284f8cf3ec5af6d7f9636229 - closing