fix: StorageProof key should be U256

[blckngm]

Motivation

According to API sepcs, storage proof keys may not be full 32-byte long:

https://github.com/ethereum/execution-apis/blob/a0d03086564ab1838b462befbc083f873dcf0c0f/src/schemas/state.yaml#L50C29-L50C29

https://github.com/ethereum/execution-apis/blob/a0d03086564ab1838b462befbc083f873dcf0c0f/tests/eth_getProof/get-account-proof-with-storage.io#L2

Solution

Change the key to U256.

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes
  This might be a breaking change. Fixing this without a breaking change will be cumbersome, by e.g. manually implementing Deserialize.

[mattsse]

@Rjected is this fixed in geth?

[blckngm]

We should still be compatible with geth since U256 can deserialize keys with or without leading zeros.

Related issue:

ethereum/go-ethereum#27306

[Rjected]

We should still be compatible with geth since U256 can deserialize keys with or without leading zeros.

yes, so deserialization should still work. serializing as a U256 should also work