Improve Static Type Checks and Error Handling in TxtinoutReader

[debpal]

This pull request includes:

• Introduced _variable_origin_static_type for static type checking of input variable origins
• Added _variable_origin_static_type in several methods of the TxtinoutReader class for general static type checking
• Removed error statements for time.sim and print.prt since errors are automatically raised by with open('time.sim') as f if the file does not exist
• Removed duplicate error checking in test functions for the TxtinoutReader class
• Removed mkdir from the copy_required_files function because it is risky: pathlib.Path(target_dir).resolve() returns an absolute path and may create files in unintended locations