ci: Packit configuration update

[LecrisUT]

Primarily some cleanups:

• Moved how the copr projects are handled. This should make it more usable if people want to use the projects to check if the spec files build well
  • Retire scikit-build-core project, instead use the auto-generated project by packit
  • Make sure nightly project is well ordered (previously they had the same NVR (name-version-release) so it would pick randomly any build from there)
• Disabled rpminspect. I will look into unifying with downstream's implementation
• Cleanups in packit.yaml to make it simpler
• Added epel-10 as a build target
• Removed python3-scikit-build-core+pyproject sub-package since it really has no effect now
• Included hatchling tests to the test environment. Postponed because F40, F39 does not satisfy requirement

---

Ideally we would want both epel-9 and epel-10 as build targets with tests enabled, but there are some issues encountered:
epel-10:

• Missing test dependencies (may be satisfied later on)

epel-9:

• Build failure because setuptools-scm can't determine version from git-archive (can be workaround)
• exceptiongroup: not packaged
  Further blocked by flit-scm -> setuptools-scm -> setuptools, the last being a major blocker for a lot of stuff getting on EPEL9
• packaging >=21.3 vs 20.9
• Missing test dependencies

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 83.90%. Comparing base (1124da7) to head (ae99525).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #799   +/-   ##
=======================================
  Coverage   83.90%   83.90%           
=======================================
  Files          74       74           
  Lines        4387     4387           
=======================================
  Hits         3681     3681           
  Misses        706      706           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.