Genvarloader

Fix

- (breaks experimental API) rename dosage to CCF and adjust alg to handle missing CCF from e.g. germline variants.

Fix

- hotfix for indexer usage

Fix

- shape of dataset return values.

Fix

- pass relevant tests.
- faster VCF reading.

Fix

- bump polars version, breaking changes upstream.

Feat

- type-safe Dataset, passes all tests.
- refactor Dataset implementation to be (almost) fully type-safe.

Fix

- Dataset.open returns highest complexity ds by default (haps + all tracks, sorted).