Create certificates with deposit values for Pools

Create two new certificates, just like `RegPoolTxCert` and `RetirePoolTxCert`, but with values for deposit and refund.

This would be nice to have in Conway, but is not a requirement.

Start by reading the existing RegPoolTxCert and RetirePoolTxCert definitions in the ledger code and trace how pool certificates are represented. Determine the Conway-specific scope and identify where deposit and refund values belong; done means two analogous certificates exist with those values represented consistently.

Written by the indexing model from the issue text.