[Go/No-Go] ARC-0037 - Introduce withdrawal address for stakers

[raychu86]

Motivation

This PR implements withdrawal addresses that staker can use claim their unbonded credits in accordance to ARC-0037.

Validators and delegators now need to specify an additional withdrawal_address when they call bond_public. While they are bonded this withdrawal address can not be changed, which is important because a core reason for this separation of addresses is so that the validator funds are secure even if their "hot" keys are compromised. This withdraw address will receive the credits that are unbonded by the staker in claim_unbond_public.

This is done with the following changes:

• Added a new withdraw mapping

  • Key: staker address
  • Value: withdrawal address

• Updated bond_public:

  • Add additional withdrawal address as input
  • Check if withdrawal_address exists in the withdraw mapping:
    • true -> Check that the withdrawal address is consistent with the one in the mapping (if it already exists)
    • false -> Update the withdraw mapping.

• Updated claim_unbond_public:

  • This is still called by the staker.
  • Withdraw the balance to the withdrawal_address
  • Remove the withdraw address if the bonded entry no longer exists for the staker

• UpdatedBondedBalances:

  • Add a withdrawal address field
  • Update atomic_pre_ratify to process the withdrawal addresses
  • Allows specifying withdrawal addresses in the genesis block

Test Plan

Tests have been added to ensure that:

• The withdrawal address receives the claimed unbonded credits.
• The withdrawal address can't be changed unless the staker is completely unbonded.
• Stakers can't call bond_public with a different withdrawal address that was was set in the withdraw mapping.
• The processing of Ratify::Genesis is correct with the new withdrawal addresses.

Additional Notes

• A staker must be completely unbonded before they are able to change their withdrawal address
• Withdrawal addresses can't be changed once initial stake is bonded

Related PRs

The sister PR can be found here - https://github.com/AleoHQ/snarkOS/pull/3165

[ljedrz]

LGTM so far 👍.

[vicsn]

Just some nits