Speed up with some native code

[mkg20001]

Some functions use JS modules as there is no native function exposed by nodeJS.
Currently I'm developing https://github.com/mkg20001/c-libp2p-crypto which could be integrated in this module to replace some of the non-native code to further improve performance.

[dryajov]

This needs to work in the browser as well, we should compile c-libp2p-crypto to wasm.

[mkg20001]

Should work but if it doesn't we can always just fallback to what's currently used.

[dignifiedquire]

This would need detailed analysis of speed and size impact, I have seen a lot of emscripten work be not faster or same speed + massive bundle size increase, both of which we want to avoid.

Also https://github.com/libp2p/rust-libp2p is coming along nicely and compiling to webassembly, might be easier to reuse what they have once that is fully working.