Make test suite run on tox v4

[johannaengland]

Scope and purpose

#399 needs to merged first.

Reference links:
https://tox.wiki/en/latest/upgrading.html
Using tox run instead of tox: https://tox.wiki/en/latest/upgrading.html#updating-usage-with-e
Setting package = editable instead of usedevelop = True: https://tox.wiki/en/latest/config.html#package
Conflict when using skipdist = True and usedevelop = True: tox-dev/tox#2730

Contributor Checklist

Every pull request should have this checklist filled out, no matter how small it is.
More information about contributing to Zino can be found in the
README.

• Added a changelog fragment for towncrier
  • not visible to user
• Added/amended tests for new/changed code
• Added/changed documentation
• Linted/formatted the code with black, ruff and isort, easiest by using pre-commit
• The first line of the commit message continues the sentence "If applied, this commit will ...", starts with a capital letter, does not end with punctuation and is 50 characters or less long. See https://cbea.ms/git-commit/

[github-actions]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time

See detailed report in MegaLinter reports
Set VALIDATE_ALL_CODEBASE: true in mega-linter.yml to validate all sources, not only the diff

[github-actions]

Test results

    4 files      4 suites   1m 48s ⏱️
  660 tests   660 ✅ 0 💤 0 ❌
2 576 runs  2 572 ✅ 4 💤 0 ❌

Results for commit 0e19fe4.

♻️ This comment has been updated with latest results.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 98.59%. Comparing base (bd1cf17) to head (0e19fe4).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #401   +/-   ##
=======================================
  Coverage   98.59%   98.59%           
=======================================
  Files          83       83           
  Lines       10021    10021           
=======================================
  Hits         9880     9880           
  Misses        141      141           

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud