Add crypto hmac sha 256

[ewalk153]

Description of the change

Running crypto functions in Javascript quickly runs out of fuel, which rust is must more efficient at the job. This is a wrapper to expose the rust hmac-sha256 implementation to javy user code.

Why am I making this change?

To conserve fuel when running crypto. As a bonus, the crypto function is not left to end users to get right.

Checklist

• [ ] I've updated the relevant CHANGELOG files if necessary. Changes to javy-cli and javy-core do not require updating CHANGELOG files.
• [ ] I've updated the relevant crate versions if necessary. Versioning policy for library crates
• [ ] I've updated documentation including crate documentation if necessary.

[ewalk153]

This code still need a change log entry, on top of any polished suggested during code review.

[saulecabrera]

The cargo vet failures are expected, since you're introducing new dependencies. We can resolve those once we're getting close to merging this one.