added associatedEntity field

[Priyanshu0109]

This change introduces key-aware filtering capabilities into the core evaluation engine by passing the evaluation key down to the filter execution layer. This is achieved by adding a generic associatedEntity field to the ConditionEngine and ConditionalMatcher interfaces, which is then populated with the current evaluation key in BonsaiTree.

This enhancement is foundational for enabling new filter Uniform Sampling Filter.

Bonsai's evaluation engine is the only component with direct, real-time access to the full context required for these new filter. The current key is only available within the BonsaiTree.evaluate() call stack. Placing the logic in Bonsai is efficient, as it avoids a complex and slow process of passing context back and forth with the consuming application.

[Tushar-Naik]

Lets rename all references of associatedEntity with entityMetadata (M). This terminology seems more apt.
Rest of the changes look good to go.