SMT Delegation Pools

[youkaicountry]

Implement SMT delegation pools.

SMT automated actions such as inflation should consume RCs from its pool.

[theoreticalbts]

So there are some conflicting requirements here:

• (a) We want users to be able to delegate vesting SMT's to a pool (like they can delegate Steem Power).
• (b) We want to maintain a tight bound on the number of outdel edges a user can have to avoid a potential DoS exploit.
• (c) Outdel edge CRUD's required authority should only be the pool operator, not the target (end-)user.

I think the best way to solve this is as follows:

• Limit each account to 3 outdel slots.
• Each outdel slot has an allowed delegator.
• By default, the allowed delegator of Slot 0 is the creator.
• By default, the allowed delegator of Slot 1 is the account recovery partner.
• By default, the allowed delegator of Slot 2 is either the creator or the account recovery partner.
• The (end-)user, or the user the slot is currently accessible to, can execute a (custom) operation to override the default and change that outdel slot's allowed delegator (ejecting any delegation currently using that outdel slot).