Make SignFromJson compatible with Safe Web UI

[zchn]

Currently, the SignFromJson script always use Multicall3.aggregate3 to generate the transaction to be signed, example: https://dashboard.tenderly.co/k-oplabs/project/simulator/4e4efb85-acfc-4210-9a8d-55785e0b65a1

The safe web UI uses MultiSendCallOnly.multiSend to generate the transaction to be signed if there are multiple calls: https://dashboard.tenderly.co/public/safe/safe-apps/simulator/3be84dfc-96d6-4069-bae6-6f64a6da5dbf, and no multicall at all if there is a single call: https://dashboard.tenderly.co/public/safe/safe-apps/simulator/d2177dce-db8a-4999-8ac0-38d2bebe3fd4

This FR is about changing SignFromJson so it behaves just like safe web UI, so different signers can choose to use either SignFromJson or Safe Web UI and they would still see the same domain hash and message hash.

[zchn]

input.json

[maurelian]

This is a great catch. I will include it in a PR which accompanies #42, prior to the ceremony.

[zchn]

Nice, thank you. Assigning this to you accordingly. But feel free to unassign and not work on this if this end up not blocking the extended pause upgrade and instead putting the launch date at risk