Provide a convenient way to retrieve a result type from an instruction

[Y-Nak]

It would be convenient to retrieve the result type from instructions. This functionality would also enable the FunctionBuilder to automatically insert a result value when a user adds an instruction, if desired.

The result type typically depends on the instruction's arguments (and occasionally on the ISA), making it impossible to determine statically. (In other words, a simple extension of the Inst macro would not be sufficient.)

The most straightforward approach might be to introduce a new trait and make it a super trait of the Inst trait.
While I haven't fully explored this approach yet, I’m creating this issue as a placeholder for further discussion and consideration.