Automate Conway update deposit scenario

[mkoura]

1. Shelley era: the user registered a stake key and paid the deposit. Let's assume it was configured in the protocol params to 2 ADA.
2. Network upgrades to Conway era.
3. A governance action updates the protocol parameters key deposit to 3 ADA
4. Conway era: the user deregisters the stake key
   a. Shelley Deregistration certificate: should the user use 2ADA or 3ADA deposit return when computing the change?
   b. Conway Deregistration certificate: should the user configure deposit value to 2ADA or 3ADA?

The problem could also be simplified to a pre-conway scenario:

5. User registers stake key (2 ADA key deposit )
6. Protocol parameters are updated -> 3 ADA key deposit.
7. User deregisters stake key -> does the user get 2ADA or 3ADA back?