`Argument.Arity` modify internal state on first get access.

[PetSerAl]

Argument.Arity modify internal state on first get access:

command-line-api/src/System.CommandLine/Argument.cs

Lines 35 to 43 in 7a5ab9e

	get
	{
	if (!_arity.IsNonDefault)
	{
	_arity = ArgumentArity.Default(this, FirstParent);
	}
	return _arity;
	}

This behavior can be problematic with debugger. As debugger display value for property it would be fixed with possibly incorrect value. Argument should define debugger view that does not initialize Arity on first get access.