Migrate shared crate off of ethcontract

[jmg-duarte]

Description

Migrates the shared crate off of ethcontract, dependency becomes based on ethrpc (which will be changed next)

Had to add an extra function to make this last one work before removing that API and others related to the old web3 library.

Changes

• Migrate the last APIs on shared to alloy
• Added erased to ethrpc to ease the transition — will be removed later

How to test

Existing tests

[gemini-code-assist]

Code Review

This pull request successfully migrates the shared crate off of ethcontract, replacing it with alloy types and functions. The changes are clean and consistent, including the removal of the ethcontract dependency, updating use statements, and refactoring code to use alloy's idioms like U256::ONE and U256::MAX.

A temporary erased function has been added to ethrpc to facilitate this transition, and it is well-documented as a short-term hack. The rest of the changes correctly adapt to the new alloy-based types, removing now-unnecessary conversions. The code is more idiomatic and consistent after these changes. Overall, this is a solid refactoring effort with no apparent issues.