Storage chains: indexing, renewals and reference counting (#8265)

* Transaction indexing

* Tests and fixes

* Fixed a comment

* Style

* Build

* Style

* Apply suggestions from code review

Co-authored-by: cheme <emericchevalier.pro@gmail.com>

* Code review suggestions

* Add missing impl

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* impl JoinInput

* Don't store empty slices

* JoinInput operates on slices

Co-authored-by: cheme <emericchevalier.pro@gmail.com>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/primitives/state-machine/src/ext.rs

@@ -18,7 +18,7 @@
 //! Concrete externalities implementation.
 
 use crate::{
-	StorageKey, StorageValue, OverlayedChanges,
+	StorageKey, StorageValue, OverlayedChanges, IndexOperation,
 	backend::Backend, overlayed_changes::OverlayedExtensions,
 };
 use hash_db::Hasher;
@@ -568,6 +568,36 @@ where
 		}
 	}
 
+	fn storage_index_transaction(&mut self, index: u32, offset: u32) {
+		trace!(
+			target: "state",
+			"{:04x}: IndexTransaction ({}): [{}..]",
+			self.id,
+			index,
+			offset,
+		);
+		self.overlay.add_transaction_index(IndexOperation::Insert {
+			extrinsic: index,
+			offset,
+		});
+	}
+
+	/// Renew existing piece of data storage.
+	fn storage_renew_transaction_index(&mut self, index: u32, hash: &[u8], size: u32) {
+		trace!(
+			target: "state",
+			"{:04x}: RenewTransactionIndex ({}) {} bytes",
+			self.id,
+			HexDisplay::from(&hash),
+			size,
+		);
+		self.overlay.add_transaction_index(IndexOperation::Renew {
+			extrinsic: index,
+			hash: hash.to_vec(),
+			size
+		});
+	}
+
 	#[cfg(not(feature = "std"))]
 	fn storage_changes_root(&mut self, _parent_hash: &[u8]) -> Result<Option<Vec<u8>>, ()> {
 		Ok(None)