types of entity creation keys and query result keys should match

[matthiaszimmermann]

depending on the context entity keys are represented as GenericBytes or str (see examples below). it would feel more consistent if entity keys would be defined as GenericBytes in both cases.

entity key in CreateEntityReturnType: [CreateEntityReturnType(expiration_block=513, entity_key=GenericBytes(0xa0fdcf49ac0c64b47e35a7fe989a76c8fff81f49898b42f73a784469d1c60f13))]

entity key in QueryEntitiesResult: [QueryEntitiesResult(entity_key='0xa0fdcf49ac0c64b47e35a7fe989a76c8fff81f49898b42f73a784469d1c60f13', ...