Implement allele remapping for arrays with `alleles`/`alt_alleles`/`genotypes` dims

[tomwhite]

Equivalent to VCF Number R/A/G.

Remove the limitation here:

vczstore/vczstore/normalise.py

Lines 84 to 90 in 2c3288d

	if dim in ("alleles", "alt_alleles", "genotypes") or dim.startswith(
	"local_"
	):
	raise NotImplementedError(
	f"Allele remapping not supported for dim {dim} in "
	f"variable {var}"
	)