Fast sync (#8884)

* State sync

* Importing state fixes

* Bugfixes

* Sync with proof

* Status reporting

* Unsafe sync mode

* Sync test

* Cleanup

* Apply suggestions from code review

Co-authored-by: cheme <emericchevalier.pro@gmail.com>
Co-authored-by: Pierre Krieger <pierre.krieger1708@gmail.com>

* set_genesis_storage

* Extract keys from range proof

* Detect iter completion

* Download and import bodies with fast sync

* Replaced meta updates tuple with a struct

* Fixed reverting finalized state

* Reverted timeout

* Typo

* Doc

* Doc

* Fixed light client test

* Fixed error handling

* Tweaks

* More UpdateMeta changes

* Rename convert_transaction

* Apply suggestions from code review

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

* Apply suggestions from code review

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

* Code review suggestions

* Fixed count handling

Co-authored-by: cheme <emericchevalier.pro@gmail.com>
Co-authored-by: Pierre Krieger <pierre.krieger1708@gmail.com>
Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/primitives/blockchain/src/backend.rs

@@ -269,12 +269,14 @@ pub struct Info<Block: BlockT> {
 	pub finalized_hash: Block::Hash,
 	/// Last finalized block number.
 	pub finalized_number: <<Block as BlockT>::Header as HeaderT>::Number,
+	/// Last finalized state.
+	pub finalized_state: Option<(Block::Hash, <<Block as BlockT>::Header as HeaderT>::Number)>,
 	/// Number of concurrent leave forks.
 	pub number_leaves: usize
 }
 
 /// Block status.
-#[derive(Debug, PartialEq, Eq)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
 pub enum BlockStatus {
 	/// Already in the blockchain.
 	InChain,

substrate/primitives/blockchain/src/error.rs

@@ -90,8 +90,8 @@ pub enum Error {
 	#[error("Failed to get runtime version: {0}")]
 	VersionInvalid(String),
 
-	#[error("Genesis config provided is invalid")]
-	GenesisInvalid,
+	#[error("Provided state is invalid")]
+	InvalidState,
 
 	#[error("error decoding justification for header")]
 	JustificationDecode,