Refactor to use variation-normalizer Python library

[theferrit32]

• Update handlers for Allele, CopyNumberCount, CopyNumberChange to use methods in the variation-normalization code
• Update worker threading to add a per-worker event loop

This does change the prereqs for running this process.

The VICC-customized UTA must be used as it adds a table which is referenced in some operations by the variation-normalization code. The compose.yaml below includes this and it includes a necessary gene-normalizer dynamodb server. Change the local ports as necessary to avoid collisions.

https://github.com/cancervariants/variation-normalization/blob/0.15.0/compose.yaml

It also makes some changes to add an asyncio event loop to each worker process so they can execute calls into the async variation-normalization functions. A future feature here may be to update our code to use asyncio.