Index alternative names for GeoNames region

We currently index only the canonical name for GeoNames regions but not any alternative names. But we do include those when searching for exact matching when matching stringly-typed regions. This has unfortunate consequences like "Deutschland" being matched to the canonical name "Federal Republic of Germany" so that searching for region:"Federal Republic of Germany" works but region:Deutschland does not.

We should amend our indexing logic to also consider the alternative names like Tag::with_token already does.