Consolidate and deduplicate MMR API methods (#12530)

* histor. batch proof: make best block arg optional

* correct testing range

* make generate_batch_proof stub for historical

* merge generate_{historical_}batch_proof functions

* merge generate_{batch_}proof functions

* merge verify_{batch_}proof functions

* merge verify_{batch_}proof_stateless functions

* remove {Leaf}Proof

Not utilized by API anymore, so superfluous.
Removal consistent with prior changes to just use "batch" proof API.

* rename BatchProof->Proof

no need to qualify if only one universal proof type.

* cleanup

* expose verify_proof rpc api

* document verify_proof

* expose verify_proof_stateless rpc api

* add optional BlockHash to mmr_root rpc api

* fixup! expose verify_proof rpc api

* fix documentation phrasing

Co-authored-by: Adrian Catangiu <adrian@parity.io>

* documentation grammar

Co-authored-by: Adrian Catangiu <adrian@parity.io>

* define mmr error msgs together with error enum

Co-authored-by: Serban Iorga <serban@parity.io>

* fixup! define mmr error msgs together with error enum

* map decoding errors to CallError::InvalidParams

Co-authored-by: Serban Iorga <serban@parity.io>

* fixup! map decoding errors to CallError::InvalidParams

Co-authored-by: Adrian Catangiu <adrian@parity.io>
Co-authored-by: parity-processbot <>
Co-authored-by: Serban Iorga <serban@parity.io>

substrate/primitives/beefy/src/mmr.rs

@@ -64,7 +64,7 @@ pub struct MmrLeaf<BlockNumber, Hash, MerkleRoot, ExtraData> {
 	pub leaf_extra: ExtraData,
 }
 
-/// A MMR leaf versioning scheme.
+/// An MMR leaf versioning scheme.
 ///
 /// Version is a single byte that constist of two components:
 /// - `major` - 3 bits