Extend translator methods

The current translator methods can only return Alleles with Literal Sequence Expressions. There is plenty of work in the [Variation Normalizer](https://github.com/cancervariants/variation-normalization) for representing HGVS expressions as Alleles that aren't bound to a Literal Sequence Expression state. It can also represent HGVS expressions as Relative and Absolute Copy Number variation. I'd like to move over this work in Variation Normalizer to vrs-python. For expressions that require some inference to be made, I plan on creating a new class(es).