feat: add option to move avg CPU to another row

[zebp]

Description

Adds an average_cpu_row option to move the average CPU usage to its own row when using basic mode.

Issue

I didn't make an issue for this, I did this for myself but thought I might as well try to upstream.

Testing

Tested by turning on and off the new layout via cli flag and config file entry and ensuring the layout was rendered accordingly.

• [x] Windows
• [x] macOS
• [x] Linux

Checklist

• [x] Areas your change affects have been linted using rustfmt (cargo fmt)
• [x] The change has been tested and doesn't appear to cause any unintended breakage
• [x] Documentation has been added/updated if needed (README.md, help menu, doc pages, etc.)
• [ ] The pull request passes the provided CI pipeline
• [x] There are no merge conflicts
• [x] If relevant, new tests were added (don't worry too much about coverage)

[zebp]

CI passes for the most part, the only failures are codecov ratelimiting

[ClementTsang]

Sorry for the delay - I'll look at it by the weekend.

the only failures are codecov ratelimiting

Yep, that's fine.