parsers: add Prefixed for prefix operator chains

[rameel]

Add Prefixed(op, reduce) for stacked prefix operators such as -, ! or ~ in front of an operand.

using static Ramstack.Parsing.Parser;

var unary = Literal
    .Number<int>()
    .Prefixed(
        OneOf("-~"),
        (value, op) => op == '-' ? -value : ~value);

unary.Parse("5").Value;   // 5
unary.Parse("-~5").Value; // 6, i.e. -(~5)

• Operators are applied from right to left, so -~5 is -(~5).
• Without operators the operand is returned as is.