Stronger typing

[timbernat]

Feel the need to strengthen typing and tyehints in a handful of places:

• gentutils.typetools : Replace custom Numeric type with builtin numbers.Number
• genutils.typetools.numpytypes : Implement arithmetic operation into array size generics (“N”, “M”, etc.) to allow arithmetic in annotations (e.g. NDArray[Shape[N/2, M**2], int] ). Relevant starting points can be found in PEP 646
• genutils.decorators.meta : Add detailed type signature transfer to all meta-decorators
• genutils.decorators.functional : Fix TypeErrors raised by Callables modified with optional_in_place decorator when passing positional-only args as kwargs
• openfftools.boxvectors: most of the type-checking here could be migrated to genutils.typetools.numpytypes, while the unit checking could be migrated to unitutils