Pydantic2 and code improvements

[1.3]

Changed

• Simplified the import of SQL classes from scout.models.sql_model
• Upgraded Pydantic and Fastapi libraries and their dependencies
• Use app lifespan instead of deprecated startup `on_event'.
• Modified code to support upgraded libraries
• Rename a test file from test_d4.py to test_handle_d4.py and add 2 new tests to it
• Fix return type of get_intervals_completeness function
• Isort imports of the entire repo