support: BuildStorage methods to take self reference (#3884)

* support: BuildStorage methods to take self reference.

There is no reason to consume the GenesisConfig when using it to
initialize a new storage backend. Instead, build_storage and
assimilate_storage now operator on self references.

* Bump node runtime impl_version.

substrate/node/runtime/src/lib.rs

@@ -84,7 +84,7 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	// implementation changes and behavior does not, then leave spec_version as
 	// is and increment impl_version.
 	spec_version: 184,
-	impl_version: 184,
+	impl_version: 185,
 	apis: RUNTIME_API_VERSIONS,
 };