Support data type Int256

There are certain usages in crypto for uint256.
Worth checking to make the type a first-class citizen instead of using bytes for the calculation.

The issue names no file, test, or entry point. Start by mapping Pinot's existing data type handling and the bytes-based calculation path, then determine the required Int256 support for the crypto usages described; done means Int256 is treated as a first-class type rather than bytes.

Written by the indexing model from the issue text.