grandpa: update to finality-grandpa v0.12.0 (#5853)

* grandpa: update to v0.12.0

* grandpa: fix tests

* grandpa: better validation of authority set invariants

* grandpa: avoid duplicating invalid authority list check

* grandpa: add missing doc

* grandpa: better validation of expect proofs

* grandpa: fix test compilation

* grandpa: fix tests

* grandpa: add test for AuthoritySet invariants

* grandpa: bump finality-grandpa to v0.12.0

substrate/Cargo.lock

@@ -1346,10 +1346,11 @@ dependencies = [
 
 [[package]]
 name = "finality-grandpa"
-version = "0.11.2"
+version = "0.12.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "024517816630be5204eba201e8d1d405042b1255a5e0e3f298b054fc24d59e1d"
+checksum = "9d7907cc24468e29b5d3ea2097e78104492b6650c55f96af1f14e7915dc155ad"
 dependencies = [
+ "either",
  "futures 0.3.4",
  "futures-timer 2.0.2",
  "log",
@@ -6344,6 +6345,7 @@ name = "sc-finality-grandpa"
 version = "0.8.0-dev"
 dependencies = [
  "assert_matches",
+ "derive_more",
  "env_logger 0.7.1",
  "finality-grandpa",
  "fork-tree",