Generalised request flat encoding changes

[jframe]

Update generalised request encoding for changes introduced in devnet4

• EIP-7251: change request to flat encoding Update EIP-7251: change request to flat encoding ethereum/EIPs#8857
• EIP-6110: change request to flat encoding Update EIP-6110: change request to flat encoding ethereum/EIPs#8856
• EIP-7002: change request to flat encoding Update EIP-7002: change request to flat encoding ethereum/EIPs#8855
• EIP-7685: change requests hash to flat hash Update EIP-7685: change requests hash to flat hash ethereum/EIPs#8854
• EIP-7685: group requests into request-data Update EIP-7685: group requests into request-data ethereum/EIPs#8924
• Make execution requests a sidecar, take 2 engine: Make execution requests a sidecar, take 2 ethereum/execution-apis#591

[macfarla]

related to #7671