PoA warp implementation (#5488)

* separate modules for consensus snapshot chunks

* bulk of authority warp logic

* finish authority warp implementation

* squash warnings and enable authority snapshot mode

* test harness for PoA

* fiddle with harness

* epoch generation proof fixes

* update constructor code

* store epoch transition proof after block commit

* basic snap and restore test

* use keyvaluedb in state restoration

* decompress chunks

* fix encoding issues

* fixed-to-contract-to-contract test

* implement ancient block import

* restore genesis transition in PoW snapshot

* add format version method to snapshot components

* supported version numbers in snapshot_components

* allow returning of ancient epoch transitions

* genesis hash mismatch check

* remove commented code

devtools/src/random_path.rs

@@ -96,7 +96,7 @@ impl Drop for RandomTempPath {
 
 pub struct GuardedTempResult<T> {
 	pub result: Option<T>,
-	pub _temp: RandomTempPath
+	pub _temp: RandomTempPath,
 }
 
 impl<T> GuardedTempResult<T> {