This PR exposes the definitions about `Int*`. The main reason is that
the `SInt` simprocs require many of them to be exposed. Furthermore,
`decide` now works with `Int*` operations. This fixes#10631.
This PR adds lemmas for iterated conversions between finite types,
starting with something of type `Nat`/`Int`/`Fin`/`BitVec` and going
through `IntX`.
