Use Rust for starknet sign/verify/pedersen

[utay]

Problem

sign/verify/pedersen functions are CPU intensive and the current implementation uses https://github.com/indutny/elliptic which is very slow in JS.

Solution

I took a look at what we can do to improve this and there seem to be several options:

1. Use Starkware's crypto-cpp repo with their crypto.js JS bindings
2. Use https://github.com/xJonathanLEI/starknet-rs/tree/master/starknet-crypto which is a pure Rust implementation of starknet crypto operations and write our own bindings
3. Rewrite src/starkware/ in Rust with https://github.com/RustCrypto/traits/tree/master/elliptic-curve and write our own bindings

I chose option 2. as the repo is seriously maintained, has better performance and portability than starknet-cpp, and was way easier than rewriting our own stark curve.

Results ⚡

• sign took 200ms before vs 1ms now -> 200x faster
• verify took 1000ms before vs 3ms now -> 333x faster
• Test suite passed successfully in 30s before vs 2s now -> 15x faster

More serious benchmark can be done but overall it's way faster!

TODO

• Clean the code and figure out a better way to switch between the JS and the Rust implementations. An env variable? I think the JS one is still great for ease of use (no need to compile Rust) and browser support
• Add CI steps to build and ship the napi addon (dynamic library) in the JS lib

[utay]

Closing in favor of #3