Update all `what4`-related packages to to concrete computation using the `bv-sized` library for fixed (but arbitrary) sized bitvector values.
Currently, the bitvector abstract domain computations are still being done directly on raw integers; we can revisit this in the future.
Co-authored-by: Ben Selfridge <benselfridge@000279.local>
Co-authored-by: Rob Dockins <rdockins@galois.com>
