Add state sync support (#7166)

* Add state sync support

* fix incorrect test tempdir

* proto: move and update Protobuf schemas

* proto: lint fixes

* comment tweaks

* don't use type aliasing

* don't call .Error() when logging errors

* use create terminology instead of take for snapshots

* reuse chunk hasher

* simplify key encoding code

* track chunk index in Manager

* add restoreDone message for Manager

* add a ready channel to Snapshotter.Restore()

* add comment on streaming IO API

* use sdkerrors for error handling

* fix incorrect error

* tweak changelog

* syntax fix

* update test code after merge

server/mock/store.go

@@ -103,6 +103,16 @@ func (ms multiStore) SetInitialVersion(version int64) error {
 	panic("not implemented")
 }
 
+func (ms multiStore) Snapshot(height uint64, format uint32) (<-chan io.ReadCloser, error) {
+	panic("not implemented")
+}
+
+func (ms multiStore) Restore(
+	height uint64, format uint32, chunks <-chan io.ReadCloser, ready chan<- struct{},
+) error {
+	panic("not implemented")
+}
+
 var _ sdk.KVStore = kvStore{}
 
 type kvStore struct {