Remove lien support from cosmos-sdk

[JimLarson]

What is the Problem Being Solved?

Modifications were made to the cosmos-sdk x/auth module to support the lien mechanism which has been deprecated and removed from agoric-sdk (swingset side in #7608, golang side in #8988, issue #8987). Since those modifications are no longer needed, we should remove them to reduce our fork footprint and ease future cosmos-sdk upgrades.

Description of the Design

• Undo the conversion of AccountKeeper into an interface, mostly in x/auth/keeper
• Remove the *Action interfaces for vesting accounts and simplify the implementations of AddGrant, ReturnGrant, Clawback, etc. Might need to keep RewardAction? (x/auth/vesting/exported, x/auth/vesting/types)
• We might be able to remove the sdk.Context argument in VestingAccount.LockedCoins back to time.Time (x/auth/vesting, x/bank/keeper).
• Distribution hooks will still be needed for Clawback accounts, but the planned changes for BLD Boost reward interception can be dropped.

Security Considerations

Should improve things by getting closer to stock cosmos-sdk.

Scaling Considerations

N/A

Test Plan

N/A. Unit tests should suffice.

Upgrade Considerations

N/A. The account-wrapping feature was designed to not have any impact on stored state.