feat(group_theory/dihedral): add dihedral groups (#5171)
Contains a subset of the content of #1076 , but implemented slightly differently.
In #1076, finite and infinite dihedral groups are implemented separately, but a side effect of what I did was that `dihedral 0` corresponds to the infinite dihedral group.
Co-authored-by: Bryan Gin-ge Chen <bryangingechen@gmail.com>
