Remove JPMS from unit tests as a simplification

[ascopes]

Removes JPMS descriptors from unit tests as a form of simplification.

A couple of test cases become irrelevant or untestable with this change, so have been removed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.21%. Comparing base (d607b76) to head (f44f8ed).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #763      +/-   ##
==========================================
- Coverage   87.65%   87.21%   -0.44%     
==========================================
  Files          99       99              
  Lines        2948     2942       -6     
  Branches      229      229              
==========================================
- Hits         2584     2566      -18     
- Misses        316      329      +13     
+ Partials       48       47       -1     

Files with missing lines	Coverage Δ
...b/ascopes/jct/junit/AbstractCompilersProvider.java	100.00% <100.00%> (ø)

... and 3 files with indirect coverage changes