Migrate starkware/math

[thor314]

Migrate math.

Relatively self-contained, only about 300 lines of code.

[agnxsh]

https://docs.rs/num-traits/0.2.17/num_traits/ any thoughts about this? it should have the things like modular arithmetic.

[thor314]

maybe overkill; many of these methods already exist in the standard library, or are accessible through a finite-field trait, I think Arkworks is re-exporting from num_traits, might b better to use ark_ff instead unless there's a specific reason to use num-traits

[agnxsh]

sure that works as well, okay.