L2: organize each prover backend's calldata in their own structs in the OnChainProposer contract

[xqft]

Currently we take all fields as separate parameters in the verify() function:

    function verify(
        uint256 blockNumber,
        //risc0
        bytes calldata risc0BlockProof,
        bytes32 risc0ImageId,
        bytes32 risc0JournalDigest,
        //sp1
        bytes32 sp1ProgramVKey,
        bytes calldata sp1PublicValues,
        bytes calldata sp1ProofBytes,
        //pico
        bytes32 picoRiscvVkey,
        bytes calldata picoPublicValues,
        uint256[8] calldata picoProof
    ) external override onlySequencer {

(this is after #1922)
it would be nice if we had something like struct SP1Calldata struct Risc0Calldata etc containing these fields.