CI workflow: use 22.04 for codecheck, coverage

[scpeters]

🎉 New feature

Improves coverage with bullet-featherstone

Summary

In #574, some functionality is being added that depends on a version of bullet that is not available on 20.04 but is available on 22.04, macOS and windows (see https://github.com/gazebosim/gz-physics/pull/574#discussion_r1397703321). Some ifdefs are being added to support compilation on 20.04, but computing code coverage on 20.04 will be incomplete. This changes the code coverage and codecheck platforms from 20.04 to 22.04, and CI is still 🟢, so it seems like a safe change.

Test it

Observer results of GitHub workflow.

Checklist

• [X] Signed all commits for DCO
• [ ] Added tests
• [ ] Added example and/or tutorial
• [ ] Updated documentation (as needed)
• [ ] Updated migration guide (as needed)
• [ ] Consider updating Python bindings (if the library has them)
• [X] codecheck passed (See contributing)
• [X] All tests passed (See test coverage)
• [ ] While waiting for a review on your PR, please help review another open pull request to support the maintainers

Note to maintainers: Remember to use Squash-Merge and edit the commit message to match the pull request summary while retaining Signed-off-by messages.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (5e58f88) 77.77% compared to head (50b4baa) 78.68%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## gz-physics6 #578 +/- ## =============================================== + Coverage 77.77% 78.68% +0.90% =============================================== Files 143 140 -3 Lines 7295 7648 +353 =============================================== + Hits 5674 6018 +344 - Misses 1621 1630 +9 ```

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