[EIP1271] Offchain signing UI tweaks

[katspaugh]

• Signatures from the same browser should be registered immedialy (currently there's a big lag even if it's from the connected wallet)

• To sign this message, you need to collect 2 owner signatures of your Safe. -> To sign this message, collect signatures from 2 owners of your Safe
• Remove this message if the threshold is 1 (To sign this message, you need to collect 1 owner signatures of your Safe.)
• Before closing the modal after the final signature comes in, add a 0.5-1s delay so that the Confirmations list is updated and the user has a chance to see it.
• Hide this in a Message details accordion (not so useful info to an average person):