State machine call proof backend (#3945)

* drafting a proof extraction at the hashdb level (to include everything
for the 'call' proof case).

* use full proof by default (replace previous proof recorder).

* fix warnings.

* Cache value not found in proof recorder.

* Remove need or internal backend struct.

* fix type.

* doc

substrate/core/sr-api/proc-macro/src/decl_runtime_apis.rs

@@ -410,7 +410,7 @@ fn generate_call_api_at_calls(decl: &ItemTrait) -> Result<TokenStream> {
 				initialized_block: &std::cell::RefCell<Option<#crate_::BlockId<Block>>>,
 				native_call: Option<NC>,
 				context: #crate_::ExecutionContext,
-				recorder: &Option<std::rc::Rc<std::cell::RefCell<#crate_::ProofRecorder<Block>>>>,
+				recorder: &Option<#crate_::ProofRecorder<Block>>,
 			) -> std::result::Result<#crate_::NativeOrEncoded<R>, T::Error> {
 				let version = call_runtime_at.runtime_version_at(at)?;
 				use #crate_::InitializeBlock;

substrate/core/sr-api/proc-macro/src/impl_runtime_apis.rs

@@ -257,7 +257,7 @@ fn generate_runtime_api_base_structures(impls: &[ItemImpl]) -> Result<TokenStrea
 			commit_on_success: std::cell::RefCell<bool>,
 			initialized_block: std::cell::RefCell<Option<#block_id>>,
 			changes: std::cell::RefCell<#crate_::OverlayedChanges>,
-			recorder: Option<std::rc::Rc<std::cell::RefCell<#crate_::ProofRecorder<#block>>>>,
+			recorder: Option<#crate_::ProofRecorder<#block>>,
 		}
 
 		// `RuntimeApi` itself is not threadsafe. However, an instance is only available in a
@@ -300,11 +300,9 @@ fn generate_runtime_api_base_structures(impls: &[ItemImpl]) -> Result<TokenStrea
 				self.recorder
 					.take()
 					.map(|recorder| {
-						let trie_nodes = recorder
-							.borrow_mut()
-							.drain()
-							.into_iter()
-							.map(|record| record.data)
+						let trie_nodes = recorder.read()
+							.iter()
+							.filter_map(|(_k, v)| v.as_ref().map(|v| v.to_vec()))
 							.collect();
 						#crate_::StorageProof::new(trie_nodes)
 					})
@@ -339,7 +337,7 @@ fn generate_runtime_api_base_structures(impls: &[ItemImpl]) -> Result<TokenStrea
 					&Self,
 					&std::cell::RefCell<#crate_::OverlayedChanges>,
 					&std::cell::RefCell<Option<#crate_::BlockId<#block>>>,
-					&Option<std::rc::Rc<std::cell::RefCell<#crate_::ProofRecorder<#block>>>>,
+					&Option<#crate_::ProofRecorder<#block>>,
 				) -> std::result::Result<#crate_::NativeOrEncoded<R>, E>,
 				E,
 			>(