fix(network): address PR feedback on van Rossem prep
* fmt: rewrap test imports / call chains to satisfy `cargo fmt --check` (CI Lints job was failing on the previously hand-formatted blocks). * test: pin the wire shape of `GetPoolDistr2` (tag 36) and `GetDRepsDelegations` (tag 39) explicitly, so an off-by-one tag in encode/decode can no longer slip past the suite by virtue of using the same wrong constant on both sides. * api: add the four post-V_16 query helpers that mirror the existing `block_query_*!` macro pattern: `get_ledger_peer_snapshot(kind)`, `get_pool_distr_v2(maybe_pools)`, `get_stake_distribution_v2()`, and `get_dreps_delegations(set)`. Without these wrappers callers hitting a v23 node still had to construct the new `BlockQuery` variants by hand. Legacy helpers (`get_big_ledger_snapshot`, `get_pool_distr`, `get_stake_distribution`) are kept untouched for back-compat with pre-v15/v21 peers. Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>