Deprecate old `Certificate` type

[palas]

Replace usages of old Certificate for the one in experimental API while maintaining backwards-compatibility.

[github-actions]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment or this will be closed in 120 days.

[Jimbo4350]

Status update (2026-03-23)

The experimental Certificate type (Exp.Certificate) has been adopted in most of the CLI — 53 usages across the codebase.

However, 5 files still import Cardano.Api.Compatible.Certificate and need to be migrated:

1. cardano-cli/src/Cardano/CLI/Compatible/StakeAddress/Run.hs
2. cardano-cli/src/Cardano/CLI/Compatible/StakePool/Run.hs
3. cardano-cli/src/Cardano/CLI/Compatible/Transaction/Run.hs
4. cardano-cli/src/Cardano/CLI/EraBased/Governance/GenesisKeyDelegationCertificate/Run.hs
5. cardano-cli/src/Cardano/CLI/EraBased/Governance/Run.hs