Unify rounding modes

[desmonddak]

Motivation

It would be nice to have the same options for rounding for both fixed and float operations by using our enum for rounding modes.
Right now we have ofDouble and ofDoubleUnrounded for the floating point type, and just ofDouble for the fixed-point.

Desired solution

Floating and fixed-point should have a parallel API that passes in the type of rounding.

Also, the other rounding modes need implementation. Right now we have truncation and RNE supported in various places, both on the Logic side as well as the value side. These should all be combed out so they are parallel and uniform to lead to a least-surprise API.

We are working on a refactoring of the FPV API to remove some of the boilerplate and factory constructors, but this feature could be added after that is complete to help further simplify the API on the value side.

Alternatives considered

No response

Additional details

No response