[AIP-123] The Great v2 to v3 Migration

Summary

The Great v2 to v3 Migration Alchemix v2 and v3 work in fundamentally different ways. If v2 continued alongside v3, it would degrade the v3 experience—debt originated in v2 would redeem positions in v3, exposing v3 users to redemptions while v2 users are not. For v3 to live, v2 must die. To achieve this, we propose a full version migration for all existing users. ## Migration Process | Step | Description | |------|-------------| | 1 | Shut down v2 via contract upgrade that disables...