Forward port blake2 storage support (#2360)

* move storage maps to blake2_128 (#2268)

* remove default hash, introduce twox_128 and blake2

* use blake2_128 & create ext_blake2_128

* refactor code

* add benchmark

* factorize generator

* fix

* parameterizable hasher

* some fix

* fix

* fix

* fix

* metadata

* fix

* remove debug print

* map -> blake2_256

* fix test

* fix test

* Apply suggestions from code review

Co-Authored-By: thiolliere <gui.thiolliere@gmail.com>

* impl twox 128 concat (#2353)

* impl twox_128_concat

* comment addressed

* fix

* impl twox_128->64_concat

* fix test

* Fix compilation and cleanup some docs

* Apply suggestions from code review

Co-Authored-By: bkchr <bkchr@users.noreply.github.com>

substrate/srml/metadata/src/lib.rs

@@ -253,17 +253,30 @@ impl std::fmt::Debug for DefaultByteGetter {
 	}
 }
 
+/// Hasher used by storage maps
+#[derive(Clone, PartialEq, Eq, Encode)]
+#[cfg_attr(feature = "std", derive(Decode, Debug, Serialize))]
+pub enum StorageHasher {
+	Blake2_128,
+	Blake2_256,
+	Twox128,
+	Twox256,
+	Twox64Concat,
+}
+
 /// A storage function type.
 #[derive(Clone, PartialEq, Eq, Encode)]
 #[cfg_attr(feature = "std", derive(Decode, Debug, Serialize))]
 pub enum StorageFunctionType {
 	Plain(DecodeDifferentStr),
 	Map {
+		hasher: StorageHasher,
 		key: DecodeDifferentStr,
 		value: DecodeDifferentStr,
 		is_linked: bool,
 	},
 	DoubleMap {
+		hasher: StorageHasher,
 		key1: DecodeDifferentStr,
 		key2: DecodeDifferentStr,
 		value: DecodeDifferentStr,
@@ -312,8 +325,10 @@ pub enum RuntimeMetadata {
 	V1(RuntimeMetadataDeprecated),
 	/// Version 2 for runtime metadata. No longer used.
 	V2(RuntimeMetadataDeprecated),
-	/// Version 3 for runtime metadata.
-	V3(RuntimeMetadataV3),
+	/// Version 3 for runtime metadata. No longer used.
+	V3(RuntimeMetadataDeprecated),
+	/// Version 4 for runtime metadata.
+	V4(RuntimeMetadataV4),
 }
 
 /// Enum that should fail.
@@ -336,7 +351,7 @@ impl Decode for RuntimeMetadataDeprecated {
 /// The metadata of a runtime.
 #[derive(Eq, Encode, PartialEq)]
 #[cfg_attr(feature = "std", derive(Decode, Debug, Serialize))]
-pub struct RuntimeMetadataV3 {
+pub struct RuntimeMetadataV4 {
 	pub modules: DecodeDifferentArray<ModuleMetadata>,
 }