BigInt wrapper and local types

[austinabell]

• Implements Wrapper for BigInt type #130

Will leave as draft until agreed upon. Another option is to just alias the Bigint types through this crate without wrapping it just to keep consistent version and allowing it to be more easily changed if custom functionality is needed in future.

All of this is optional but seeing interactions needed in the near future, for example Cbor encoding, let me know if you guys want this.

I only changed usage in the vm package as well for this, since no one else is modifying, and can change the other references once agreed upon and probably in a seperate PR

[austinabell]

Just going to close this for now, if we need to add our own functionality on this type can just use these changes as a template to reimplement.