feat: Adapt to new types introduced in fiat-crypto 0.2

[divergentdave]

I have an outstanding PR that proposes some breaking changes to fiat-crypto, see mit-plv/fiat-crypto#1623. Briefly, it introduces new structures to replace type aliases, to prevent misuse of functions with different preconditions on their inputs' ranges. I'm opening this PR for a future upgrade early, with a [patch.crates-io] stanza, to kick the tires on the breaking change, and for temporary use in fiat-crypto integration tests. If this looks good, I can back out the patch stanza when fiat-crypto is released and mark it ready for review.

[kevaundray]

This looks good to me, once fiat-crypto is released, please ping me!

[divergentdave]

It's out now, I've removed the pinned git commit