EVM runtime: Consider uint alternative

[mriise]

uint crate makes it's bigints from u64, which won't be as efficient as using u32 in wasm32 (collections of u32 may also be faster on x86 due to cache line sizes, but is irrelevant here).

https://github.com/RustCrypto/crypto-bigint provides bigints with pointer-sized words and constant time operations as a bonus

[karim-agha]

bad idea.

[Stebalien]

wasm32 isn't like x86. It has native support for 64 bit integers and will lower those operations to native 64bit instructions.