CDDL specs for ledger state queries

[nfrisby]

The Consensus Layer defines Node-to-Client queries over the LocalStateQuery mini protocol. This is how the CLI and other such separate tools ask the node about its current state.

For the most part, those Consensus Layer queries and their logic are simply wrappers around some ledger code. In particular, this includes the codecs for those query arguments and their responses.

Therefore, this Issue is to specify the CDDL for data structures involved in the arguments of NTC queries and responses.