Use Transformations instead of GufeKeys for StrategyResults

[ianmkenney]

Related Issues

Fixes #15

Description

This PR changes how Transformations and their weights are represented within a StrategyResult instance. Previously, the _weights attribute was a dictionary with GufeKeys as keys and Optional[float] as values. Since we should not assume GufeKeys are stable, we should keep track of Transformations directly instead.

However, since Transformations cannot be used as dictionary keys (see OpenFreeEnergy/gufe#714), the mapping needs to be internally represented in a compatible format. Instead of dict[Transformation | NonTransformation, float | None], we'll instead use list[list[Transformation | NonTransformation, float | None]].

Inputs to init and outputs of resolve are still dictionaries, though their keys are now Transformations, not GufeKeys

Changes

• All instances of GufeKey in signatures are changed to Transformation | NonTransformation
• New validation method for StrategyResult that checks types of keys and values of input mapping. Failure to validate raises StrategyResultValidationError.
• Initialization weights parameter and resolve return are now of type dict[Transformation | NonTransformation, float | None].

Checklist

• Documentation updated
• Added or modified tests