feat: EraHistory ledger query

[agaffney]

Fixes #321

[agaffney]

NOTE: query tip uses the EraHistory query (as well as a few others) under the hood

$ cardano-cli latest query tip --socket-path ~/dev/blinklabs-io/dingo/dingo.socket --testnet-magic 2
{
    "block": 3047908,
    "epoch": 870,
    "era": "Conway",
    "hash": "13625033d07cf27be145447cd10f5812a26c3bdca9a0dd0def4fb1636ad8f315",
    "slot": 75242243,
    "slotInEpoch": 74243,
    "slotsToEpochEnd": 12157,
    "syncProgress": "100.00"
}