F16 support

[lillianrubyrose]

Wife and I want Zfh & Zfhmin support in whisker so here this is~

I'm making this as a draft PR before I'm done for a few reasons. so I don't forget about it but also to ask a few questions:

1. What do you think about getting this uploaded to crates.io? Is there any specific reason you haven't done so already?

2. What do you think about splitting the wrapper into a feature or separate crate?
   For me it's just a preference thing as I plan to write my own thin wrapper sometime for whisker and the wrapper uses num-traits which I would prefer not to pull in if I'm not actively using it.

(note: Before I mark for review I'll squash everything down to a single commit and force-push, it's just easier for me to track things this way for now 💜)

[HarryR]

Hey this is super cool!

What do you think about getting this uploaded to crates.io? Is there any specific reason you haven't done so already?

• Yup will get this on crates.io with proper versioning, only reason was that only I was using it.

What do you think about splitting the wrapper into a feature or separate crate?

• Hmm, num-traits and dependencies, you have a good point. I can separate the crates.

I have time this week to get more testing setup, the CI at the moment is only testing f32, but I need to manually run the full conformance suite to verify it matches testfloat (not sure if you're doing that or not). Then dig out some of my simulator code where I had some minor edge cases with RISCOF.

So my TODO would be:

• Split crates so wrapper is separate, or... use a feature for the wrapper (making num-traits optional?)
• Test stuff
• Publish on crates.io
• Check RISCOF and update my projects

Then I'm happy to add you as a collaborator on this repo if it will make your life easier in future.

[lillianrubyrose]

All comments besides the one regarding linting are just reminders for myself as I'm taking a break now.

[lillianrubyrose]

I commented these out because a lot of code that wasn't added in this PR (I'm sure tons of what I added here does as well though!) violates various lints in these groups and my editor was screaming lol.

I could fix them in this PR if you'd like, @HarryR , although I think it would be more appropriate for me to do as a follow-up PR.

[lillianrubyrose]

Hey this is super cool!

I have time this week to get more testing setup, the CI at the moment is only testing f32, but I need to manually run the full conformance suite to verify it matches testfloat (not sure if you're doing that or not).

I haven't ran any of this code against testfloat, no. I could probably get it running pretty easy on my NixOS machine but I'm currently under Windows for a little bit and that'd be rough :p.

I think I've got everything implemented relating to F16s now though, just have to figure out if it's correct or not