lastidnotfound step 2:
* move "record stage", aka poh_service into banking stage
* remove Entry.has_more, is incompatible with leader rotation
* rewrite entry_next_hash in terms of Poh
* simplify and unify transaction hashing (no embedded nulls)
* register_last_entry from banking stage, fixes#1171 (w00t!)
* new PoH doesn't generate empty ledger entries, so some fixes necessary in
multinode tests that rely on that (e.g. giving validators airdrops)
* make window repair less patient, if we've been waiting for an answer,
don't be shy about most recent blobs
* delete recorder and record stage
* make more verbost thin_client error reporting
* more tracing in window (sigh)