refactor(mypy): Finish type hint the rql/__init__.py module
- Type hint all `parse` functions inside rql/__init__.py - Create a type alias to represent what's returned by `parse` functions above - Update RQLSTChecker.check method signature: * node parameter should be a BaseNode or any children of BaseNode class - Type hint `copy_uid_node` function - Remove useless variable: pyparse = parse - Format without any compromise