Typecheck `lance/schema.py`, `lance/file.py`, `lance/util.py`

1. Add files to pyright whitelist: https://github.com/lancedb/lance/blob/c6fcb31ec6ca50797765420feb7fd704862de788/python/pyproject.toml#L74
2. Fix all type checking errors

For reference, see this PR: https://github.com/lancedb/lance/pull/3286