Attempt to make codecov less important

[kingbuzzman]

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Depends on https://github.com/pytest-dev/pytest-django/pull/1202 Related to https://github.com/pytest-dev/pytest-django/pull/1201 -- had to close it due to CI not running

This all started because yesterday codecov was having issues, and p!$#ed me off...

This PR aims to reduce the emphasis on Codecov by adjusting coverage exclusions in pyproject.toml and modifying the CI workflow to handle coverage reporting differently.

• Update pyproject.toml by excluding "pytest_django/_version.py" in both run and report configurations.
• ~Revise the CI workflow to use ubuntu-latest, update Tox versions, and introduce dedicated coverage reporting and artifact handling steps.~

Miscellaneous:

• ~CI now runs on all branches -- instead of those that were pointing to main only~
• ~Updated tox version since python 3.8 is gone!~
• Added html and the main coverage file to the archive
• Adds markdown details of coverage in the CI summary
• Moves the CI matrix up -- personal thing, i can move it back if its too many changes