Remove non-coverage tests

[JoshuaLampert]

As explained in #108 the more complex splitting between coverage and non-coverage tests should be obsolete by now. This PR removes the non-coverage tests and is based on trixi-framework/Trixi.jl#2254 (and trixi-framework/Trixi.jl#2261).

[JoshuaLampert]

With this PR, the upstream - * tests can be removed from the list of required status checks.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.34%. Comparing base (7692ca7) to head (aca0031).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #109      +/-   ##
==========================================
+ Coverage   99.30%   99.34%   +0.05%     
==========================================
  Files          82       82              
  Lines        4263     4263              
==========================================
+ Hits         4233     4235       +2     
+ Misses         30       28       -2     

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[JoshuaLampert]

Hm, I don't quite understand why coverage reports a lot of missing parts. It seems to recognize most tests, but not all.

[JoshuaLampert]

So now after rerunning CI, coverage is happy again, i.e., this is ready for review from my point of view.

[JoshuaLampert]

I think Patrick and Andrew are on vacation this week. Do you have the rights to remove the upstream - * tests from the required status checks, @ranocha? If so, maybe we could go on with merging, such that we can continue with the other PR(s) regarding moving to TrixiTest.jl?