Refactor Multisig Pallet

[shawntabrizi]

This is a PR that refactors the Multisig pallet to:

• Reduce complexity of the extrinsics
• Reduce duplicated code
• Simplify weight calculations

This PR splits the approve_as_multi and as_multi functions into clear linear steps that can be followed to complete a multi-signature operation:

1. create: Creates a multi-signature operation using the hash of the call.
2. note_preimage: Allows any sender to upload the raw call preimage for a multi-signature call hash.
3. approve: Allows anyone in the multi-signature to voice their approval for the call.
4. complete: When a multi-signature operation reaches the threshold number of approvals, this will dispatch the call using the preimage that was uploaded.
5. cancel: The original creator of the multisignature operation can close it before it is completed.

When combined with batch calls, this refactor can act just like the original pallet:

• batch(create, note_preimage): Create a multisig with some stored call preimage
• batch(approve, note_preimage, complete): The final approval of a multisig with no preimage can batch this call to complete the multisig.
• batch(create, note_preimage, complete): 1 user threshold multisig created and completed in a single transaction

In progress

[xlc]

How do you know the timepoints parameter for approve/complete for a non exist multisig request? I don't think you can use batch to reduce number of txs.

[shawntabrizi]

yes that is a good point. So you can batch anything after the initial create