* skip tests requiring specific setup (proxy, certificates) by default,
use `-P all` in CI to run all tests
* automatically cleanup temp/downloaded files in tests
* remove some logging from tests

<!-- Write down your pull request descriptions. -->

### New Pull Request Checklist

- [x] I have read the
[Documentation](https://pub.dev/documentation/dio/latest/)
- [x] I have searched for a similar pull request in the
[project](https://github.com/cfug/dio/pulls) and found none
- [x] I have updated this branch with the latest `main` branch to avoid
conflicts (via merge from master or rebase)
- [ ] I have added the required tests to prove the fix/feature I'm
adding
- [ ] I have updated the documentation (if necessary)
- [x] I have run the tests without failures
- [ ] I have updated the `CHANGELOG.md` in the corresponding package

### Additional context and info (if any)

<!-- Provide more context and info about the PR. -->