Mmr persist state (#12822)

client/mmr: persisting gadget state across runs

Fixes #12780

* client/mmr: on init do canonicalization catch-up

* client/mmr: add more tests

* client/mmr: persist gadget progress in aux db

* client/mmr: add more tests

* client/mmr: replace async_std with tokio

* remove leftover comment

* address review comments

Signed-off-by: acatangiu <adrian@parity.io>

substrate/Cargo.lock

@@ -4137,6 +4137,7 @@ dependencies = [
  "futures",
  "log",
  "parity-scale-codec",
+ "parking_lot 0.12.1",
  "sc-block-builder",
  "sc-client-api",
  "sc-offchain",
@@ -4148,6 +4149,7 @@ dependencies = [
  "sp-io",
  "sp-mmr-primitives",
  "sp-runtime",
+ "sp-tracing",
  "substrate-test-runtime-client",
  "tokio",
 ]