Implement byte-to-char casts for crucible-mir.

[sauclovian-g]

No description provided.

[RyanGlScott]

Thanks, @sauclovian-g! I can believe that this fixes the issue, but I would feel better if we added a regression test alongside it. Can you add this test case to crux-mir's test suite? I'm not too bothered about the exact location where we put the test—somewhere in test/conc_eval/num would work, for instance.

[RyanGlScott]

@sauclovian-g, do you plan on finishing this?

[sauclovian-g]

Yes, we need it for FV, just disorganized/behind on everything :-|

[sauclovian-g]

This should be ready to go now.

(I think I should rebase it on master before merging, and probably squash the two commits together too, but probably you should look at it first)

[RyanGlScott]

Thanks for pushing this one over the finish line!

[sauclovian-g]

I rebased it on master and squashed the commits together. Since it's small and isolated this is pretty harmless, and it's been sitting around for a while.