Implement JSON instances for the new experimental TxOut

[Jimbo4350]

The old API is being deprecated. We need to implement new JSON instances (ToJSON/FromJSON) for the new TxOut definition in the experimental API. The existing FromJSON (TxOut CtxTx era) instance is a mess and should not be carried forward — the new instances should be clean implementations against the new type.

[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.

[github-actions]

This issue is stale because it has been open 90 days with no activity. Remove stale label or comment or this will be closed in 100 days.