Cardano Updates

* Add ToJSON/FromJSON as superclass constraints to EraScript
* Add ToJSON/FromJSON instances for MultiSig, Timelock and DijkstraNativeScript
* Add structured JSON serialisation for native scripts across all eras (Shelley, Allegra, Dijkstra)
* Add FromJSON instance for AlonzoScript (hex-encoded CBOR roundtrip)
* Add EncCBOR/ToCBOR instances for PlutusScript era
* Rename kindObject (returning Value) to kindObjectValue; add new kindObject returning Aeson.Object
  * Add new kindObject returning Aeson.Object
* Fix shelleyBasedEraNativeScriptToJSON and sizedNativeScriptGens to accept a child continuation to correctly handle nested scripts across eras
* Add round-trip JSON property tests for NativeScript and Script to the shared era spec

There is no need to have a separate type class for a common concept that
we aready have for all eras that is provided by `EraTest`. This commit
also hides unnecessary for public view implementation detail:
`EraRuleProof` and `UnliftRules`.

Thanks to `EraRulesWithFailures` type family and relocation of predicate
failure CBOR roundtrip tests into `ledgerTestMain` we are guaranteed
that these tests will run for all eras. Moreover, this changes is in
line with overall tests hierarchy that we are converging onto.

Coder's SparseKeyed alternative

Introduce 'Maybe LeiosCert' (mirrored after the existing 'Maybe
PerasCert') as an optional field on the Dijkstra-era 'BlockBody'. Other
eras are unaffected — this is the entire Leios-related ledger changes
from leios-prototype at the time of the remake.

it across eras

across eras

since this is now part of the `StAnnTx` signal