Remove legacy polymake interfacing code

[fingolfin]

Instead rely on the polymaking package.

It works locally for me but fails in CI here, so clearly needs some more work.

[codecov]

Codecov Report

❌ Patch coverage is 56.75676% with 32 lines in your changes missing coverage. Please review.
✅ Project coverage is 44.73%. Comparing base (6c3d924) to head (da03ffa).
⚠️ Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
lib/Polymake/orbitPoly.gi	16.66%	25 Missing ⚠️
lib/Polymake/polyGens.gi	84.09%	7 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #136      +/-   ##
==========================================
- Coverage   44.81%   44.73%   -0.09%     
==========================================
  Files         345      345              
  Lines       64893    64760     -133     
==========================================
- Hits        29085    28971     -114     
+ Misses      35808    35789      -19     

Files with missing lines	Coverage Δ
lib/externalSoftware.gap	85.00% <ø> (-1.85%)	⬇️
lib/Polymake/polyGens.gi	78.94% <84.09%> (-10.09%)	⬇️
lib/Polymake/orbitPoly.gi	46.80% <16.66%> (-3.78%)	⬇️

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[fingolfin]

Yay, this works now, too! I had made a rather stupid mistake right at the start of the function where I reordered a loop thinking "this is equivalent but more elegant". When I looked at it again, I immediately realized that it was of course not equivalent... sigh Anyway, this is passing all tests now :-)