## Issue Addressed
Resolves#3314
## Proposed Changes
Add a module to encode/decode u256 types according to the execution layer encoding/decoding standards
https://github.com/ethereum/execution-apis/blob/main/src/engine/specification.md#structures
Updates `JsonExecutionPayloadV1.base_fee_per_gas`, `JsonExecutionPayloadHeaderV1.base_fee_per_gas` and `TransitionConfigurationV1.terminal_total_difficulty` to encode/decode according to standards
Co-authored-by: Michael Sproul <micsproul@gmail.com>