Add measurements of nucleotide dihedral angles

[padix-key]

This PR adds the nucleotide_dihedral_backbone() and nucleotide_dihedral_side_chain() functions for computing dihedral angles of nucleic acid structures.

[codspeed-hq]

Merging this PR will not alter performance

✅ 98 untouched benchmarks

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_{Comparing padix-key:nucleotide-dihedrals (0189bfe) with main (2e5ef85)}