Investigate long limbs on UInt256

[ahamlat]

Investigate using Long limbs instead of Int limbs in UInt256. The main reason is to improve performance performance and reduce code complexity.

[jflo]

are you working on this @thomas-quadratic ?

[thomas-quadratic]

Yes it has been implemented and benchmarked for some time now. A PR is coming shortly!

[macfarla]

branch on longs as limbs: https://github.com/thomas-quadratic/besu/tree/feature/uint256-long-limbs

[siladu]

Completed in #9677