feat: RNTuples with custom-length floats and suppressed columns

[ariostas]

This PR adds root files (and code to generate them) containing RNTuples with custom-length floats and suppressed columns.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 72.38%. Comparing base (ef38efa) to head (21ec32e).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #167   +/-   ##
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  Coverage   72.38%   72.38%           
=======================================
  Files           3        3           
  Lines         134      134           
=======================================
  Hits           97       97           
  Misses         37       37           

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[jpivarski]

Looks good! I'll merge it and ask at our meeting in 15 minutes whether you're ready for a new release of scikit-hep-testdata.