ICRC-153: Standardizing Privileged Freeze & Unfreeze Controls

[bogwar]

This PR introduces ICRC-523, a standard API for freezing and unfreezing accounts and principals. It defines four privileged methods, canonical tx mapping, and use of the block kinds from ICRC-123. The standard provides auditors, wallets, and integrators with a consistent way to determine whether funds are frozen and to attribute freezes/unfreezes to authorized actors.