Add U240 params

[olehmisar]

Problem

U240 would be enough for most EVM token amount operations, so in Noir it can be represented with only 2 limbs (vs 3 limbs for U256).

Happy Case

Implement bignum::fields::U240Params

Workaround

None

Workaround Description

No response

Additional Context

No response

Project Impact

Nice-to-have

Blocker Context

No response

Would you like to submit a PR for this Issue?

None

Support Needs

No response

[olehmisar]

also, would be interesting to see the benchmarks of std::U128 vs bignum::U240 as they both consist of 2 limbs(except U128 limbs are of type u64)

[TomAFrench]

Hey, before adding this we would want to see the outcomes of the token standardization work to determine whether U240 would actually be used.

Until that point, it can be instantiated outside of this library.

[olehmisar]

@TomAFrench how do I get the U240 parameters? Also, I need U253 parameters as well for the benchmarks