wgsl: Expose various test range generators in FPTraits

[zoddicus]

There are a variety of functions for generating test ranges that are effective parameterized by fp type (vectorF16Range vs vectorF32Range vs vectorF64). Because these are not part of the FPTraits there is a bunch of cases where case generation code is needing different functions instead of doing something like FP[trait].vectorRange.

dot for example was actually doing the wrong thing, and using F32 for both f32 and f16, so there are probably some bugs from this to be quashed.

This bug covers adding the APIs to FPTraits, and refactoring the existing code to use them.