Fix f_vector for cones with lineality (and the point)

[imkhln]

This resolves #5714.

I have no permission to assign but @lkastner this one's for you.

[benlorenz]

Looks like the tests are also wrong, Cone2 should indeed have [1,2] and not [0,2].

[benlorenz]

Suggested change

	ld = pmc.LINEALITY_DIM
	fv = ld == pmc.CONE_DIM ? ZZRingElem[] : pmc.F_VECTOR
	ld = lineality_dim(C)
	fv = ld == dim(C) ? ZZRingElem[] : pmc.F_VECTOR::Polymake.Vector{Polymake.Integer}

I recommend adding type assertions for polymake properties because julia cannot deduce the return type and also use the existing methods where possible.

[imkhln]

Done.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 84.04%. Comparing base (f716867) to head (d30e228).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5716      +/-   ##
==========================================
- Coverage   84.05%   84.04%   -0.01%     
==========================================
  Files         750      750              
  Lines      103019   102980      -39     
==========================================
- Hits        86591    86554      -37     
+ Misses      16428    16426       -2     

Files with missing lines	Coverage Δ
src/PolyhedralGeometry/Cone/properties.jl	90.10% <100.00%> (+0.57%)	⬆️

... and 9 files with indirect coverage changes

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