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/support/src/metadata.rs

@@ -16,10 +16,14 @@
 
 pub use srml_metadata::{
 	DecodeDifferent, FnEncode, RuntimeMetadata,
-	ModuleMetadata, RuntimeMetadataV3,
+	ModuleMetadata, RuntimeMetadataV4,
 	DefaultByteGetter, RuntimeMetadataPrefixed,
+	StorageMetadata, StorageFunctionMetadata,
+	StorageFunctionType, StorageFunctionModifier,
+	DefaultByte, StorageHasher
 };
 
+
 /// Implements the metadata support for the given runtime and all its modules.
 ///
 /// Example:
@@ -36,8 +40,8 @@ macro_rules! impl_runtime_metadata {
 	) => {
 		impl $runtime {
 			pub fn metadata() -> $crate::metadata::RuntimeMetadataPrefixed {
-				$crate::metadata::RuntimeMetadata::V3 (
-					$crate::metadata::RuntimeMetadataV3 {
+				$crate::metadata::RuntimeMetadata::V4 (
+					$crate::metadata::RuntimeMetadataV4 {
 						modules: $crate::__runtime_modules_to_metadata!($runtime;; $( $rest )*),
 					}
 				).into()
@@ -377,8 +381,8 @@ mod tests {
 			event_module2::Module with Event Storage Call,
 	);
 
-	const EXPECTED_METADATA: RuntimeMetadata = RuntimeMetadata::V3(
-		RuntimeMetadataV3 {
+	const EXPECTED_METADATA: RuntimeMetadata = RuntimeMetadata::V4(
+		RuntimeMetadataV4 {
 		modules: DecodeDifferent::Encode(&[
 			ModuleMetadata {
 				name: DecodeDifferent::Encode("system"),