Poh subsystem cleanup, genesis plumbing, enable real PoH on edge testnet (#4292)

* Remove unused PohServiceConfig::Step

* Clarify variable name

* Poh::hash() now takes an iteration counter

* man -> max

* Inline functions with single call site

* Move PohServiceConfig into GenesisBlock

* Add plumbing to enable real PoH on testnets

* Batch hashes to improve PoH hash rate

* Ensure a constant hashes_per_tick

* Remove PohEntry mixin field

* Poh/PohEntry no longer maintains tick_height

* Ensure a constant hashes_per_tick

* ci/localnet-sanity.sh: Use real PoH

* Rework Poh/PohService to keep PohRecorder unlocked as much as possible while hashing

core/src/entry.rs

@@ -171,16 +171,12 @@ fn next_hash(start_hash: &Hash, num_hashes: u64, transactions: &[Transaction]) -
         return *start_hash;
     }
 
-    let mut poh = Poh::new(*start_hash, 0);
-
-    for _ in 1..num_hashes {
-        poh.hash();
-    }
-
+    let mut poh = Poh::new(*start_hash, None);
+    poh.hash(num_hashes.saturating_sub(1));
     if transactions.is_empty() {
-        poh.tick().hash
+        poh.tick().unwrap().hash
     } else {
-        poh.record(hash_transactions(transactions)).hash
+        poh.record(hash_transactions(transactions)).unwrap().hash
     }
 }