Fix sub2eth synchronization (#172)

* ease serde version requirements (to build OE with builtin)

* trace + fix completion notifications

* check incompletion on submit

* fix compilation

* do not ask for synced blocks when queue is empty

* cargo fmt --all

* Update relays/ethereum/src/ethereum_client.rs

Co-authored-by: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* remove closure

* fn submit_substrate_header() -> Option<RpcError>

Co-authored-by: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

bridges/relays/ethereum/res/substrate-bridge-abi.json

@@ -96,6 +96,25 @@
 		"stateMutability": "view",
 		"type": "function"
 	},
+	{
+		"inputs": [
+			{
+				"internalType": "bytes",
+				"name": "rawHeader",
+				"type": "bytes"
+			}
+		],
+		"name": "isIncompleteHeader",
+		"outputs": [
+			{
+				"internalType": "bool",
+				"name": "",
+				"type": "bool"
+			}
+		],
+		"stateMutability": "view",
+		"type": "function"
+	},
 	{
 		"inputs": [
 			{