Fix all parameter type hints

[meck-gd]

• Type hints such as myparam: [int, str] are invalid. They were meant to be unions, so I changed them to int | str.
• Type hints such as myparam: int = None are also invalid; if you want to have None defaults, you'll have to be explicit and allow None as a type. Some type checkers won't flag the method definition, but if you'd like to pass all possible parameters at a call site and pass None, you'll be flagged with no way of fixing it.