Cardano Updates

This commit introduces a general hierarchy for common era testing

* Add missing changelog entries.
* Revert missing cddl section in shelley changelog.
* Convert positional args to record syntax in Examples.

Also,
* Needed some examples re-exported from conway, they seemed to have been
updated, and led to updates to the goldens.

JSON goldens should only need to test encoding, and moreover we have to
ensure that all ledger state query result types are able to be encoded:
and so the test harnesses collapse back to a single one.

Some ToJSON instances were found to be orphans in downstream packages
because ledger didn't have those instances.

* DefaultVote: from cardano-cli/src/Cardano/CLI/Orphan.hs
* StakeSnapshot, StakeSnapshots: from
cardano-api/src/Cardano/Api/Internal/Orphans/Serialisation.hs
* QueryPoolStateResult: written fresh — no prior ToJSON found across
cardano-api, cardano-cli, ouroboros-consensus, or cardano-db-sync,
including via intermediate wrapper types. Implemented here via
KeyValuePairs to match other query result types.

We run the tests to add JSON goldens for queryPoolState,
queryStakePoolDefaultVote, and queryStakeSnapshots, which the new
instances unblock.

Note: this bundles three logical changes (instance absorption, harness
collapse, 3 new goldens).

eraLedgerStateQueryGoldenSpec requires full {To,From}JSON+{Enc,Dec}CBOR.
Some query result types do not have all these instances: some lack only
FromJSON, some both {To,From}JSON.