Update workcache to no longer use Sha1.
Remove MD5 and Sha2. Move Sha1 and support code into librustpkg.
Add a comment to Sha1 that its not suitable for cryptogrpahic uses.
Remove dead code from cryptoutil.rs and remove macro_rules feature flag.
Remove MD4.
Integrate the code in the digest and cryptoutil modules directly into the sha1 module.