Replace BATCH_CALL_SUPPORTED (#1733)

* Simplify submit_and_watch_signed_extrinsic

The way submit_and_watch_signed_extrinsic is used now, we can always
derive the SignParam from other params. If in the future we need more
customization possibilities, we can define a new method.

* Simplify submit_signed_extrinsic

* Send maybe_batch_tx as a parameter

Send `maybe_batch_tx` as a parameter to `submit_proof()`. This way we
can deduplicate the logic that submits the extrinsic for
`messages_source and `messages_target` and we can simplify the logic in
the race loop a bit.

* Define BatchProofTransaction

Deduplicate BatchConfirmationTransaction and BatchDeliveryTransaction by
replacing both of them with BatchProofTransaction

* Define ChainWithUtilityPallet and BatchCallBuilderConstructor

- Define `ChainWithUtilityPallet` in order to be able to associate the
  batching functionality with chains
- Defining `BatchCallBuilderConstructor` in order to have a more reliable
  way of checking whether an end of a messages pipeline supports batching
  or no. `BatchCallBuilderConstructor::new_builder()` returns an
  `Option<BatchCallBuilder>`.This is a bit safer because each time a caller
  tries to start creating a batch call, it will call `new_builder()` and
  will be required to handle the returned `Option`. Before we only had a
  bool `BATCH_CALL_SUPPORTED` the caller could have forgetten to check.

bridges/relays/client-substrate/src/chain.rs

@@ -234,3 +234,31 @@ impl<Block: BlockT> BlockWithJustification<Block::Header> for SignedBlock<Block>
 		self.justifications.as_ref().and_then(|j| j.get(engine_id))
 	}
 }
+
+/// Trait that provides functionality defined inside `pallet-utility`
+pub trait UtilityPallet<C: Chain> {
+	/// Create batch call from given calls vector.
+	fn build_batch_call(calls: Vec<C::Call>) -> C::Call;
+}
+
+/// Structure that implements `UtilityPalletProvider` based on a full runtime.
+pub struct FullRuntimeUtilityPallet<R> {
+	_phantom: std::marker::PhantomData<R>,
+}
+
+impl<C, R> UtilityPallet<C> for FullRuntimeUtilityPallet<R>
+where
+	C: Chain,
+	R: pallet_utility::Config<RuntimeCall = C::Call>,
+	<R as pallet_utility::Config>::RuntimeCall: From<pallet_utility::Call<R>>,
+{
+	fn build_batch_call(calls: Vec<C::Call>) -> C::Call {
+		pallet_utility::Call::batch_all { calls }.into()
+	}
+}
+
+/// Substrate-based chain that uses `pallet-utility`.
+pub trait ChainWithUtilityPallet: Chain {
+	/// The utility pallet provider.
+	type UtilityPallet: UtilityPallet<Self>;
+}