refactor: implement lazy loading for heavy dependencies in Memory module (#4632)

- Introduced lazy imports for the Memory and EncodingFlow classes to optimize import time and reduce initial load, particularly beneficial for deployment scenarios like Celery pre-fork.
- Updated the Memory class to include new configuration options for aggregation queries, enhancing its functionality.
- Adjusted the __getattr__ method in both the crewai and memory modules to support lazy loading of specified attributes.