Reduce number of dependencies of llrt_crypto

The module has too many dependencies, it really pollutes any project trying to import it since some have very deep web of dependencies. For example we pull in two different bigint implementations (`num-bigint-dig` and `crypto-bigint`)
We have a lot of duplicate with ring anyway and we should prefer using it. Curve crypto is still not in ring, but planned (https://github.com/briansmith/ring/issues/1771)

Start by inspecting the llrt_crypto dependency declarations and generating its dependency tree to identify duplicate bigint implementations and overlap with ring. Review which curve-cryptography features still require non-ring dependencies; done means reducing redundant dependencies without removing required curve support.

Written by the indexing model from the issue text.