Add dihedral_side_chain()

[padix-key]

This PR adds dihedral_side_chain() which analogous to dihedral_backbone() computes the side chain dihedral angles of amino acid residues. Furthermore the residue-level functions get_atom_name_indices() and get_all_residue_positions() are added.

[codspeed-hq]

CodSpeed Performance Report

Merging #827 will improve performances by 35.48%

_{Comparing padix-key:chi-dihedrals (830fc43) with main (6268d59)}

Summary

⚡ 3 improvements
✅ 56 untouched

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
⚡	benchmark_structural_alphabet_methods[to_3di]	13.1 ms	10.3 ms	+27.18%
⚡	benchmark_structural_alphabet_methods[to_protein_blocks]	8.9 ms	6.5 ms	+35.48%
⚡	benchmark_superimpose[superimpose_structural_homologs]	39.4 ms	32.5 ms	+21.23%