feat(typing): make types more precise for many common Values

[NickCrews]

This partially mitigates #11680, at least for some of the more common types.

In particular, it solves this ask:
#11680 (comment)

I focused on the most common use cases, eg StringValue + "foo" is more important than NumericColumn.kurtosis()

This fixes several sorts of problems:

• It types methods as returning the right datashape. Sometimes this was as simple as use Self, but often this required @overload because the method depends on the datashape of second args, or it is an eg string->int method
• It make datatypes more precise in some places, eg before it was simply returning NumericValue, but we actually know it is FloatingScalar
• It fixes the typing in some places. eg in StringValue.__getitem__, it actually accepts IntegerColumn as well, not just IntegerScalar, as it was typed before. Or IntegerValue.convert_base() incorrectly said it returned a IntegerValue, but it actually returns a StringValue