Parachain validation moved to external process (#325)

* Improved execution & tests

* Style

* Made CLI arg const

* Moved Upwards message

* CLI subcommand for validation worker

* Build halting parachain

* Build halting parachain

* Made stuff private

* Reorganized parachain tests

* Comment

* Whitespace

* Apply suggestions from code review

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* Fixed call data size check and introduced an enum

* Apply suggestions from code review

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

polkadot/collator/src/lib.rs

@@ -429,12 +429,11 @@ fn compute_targets(para_id: ParaId, session_keys: &[SessionKey], roster: DutyRos
 ///
 /// Provide a future which resolves when the node should exit.
 /// This function blocks until done.
-pub fn run_collator<P, E, I, ArgT>(
+pub fn run_collator<P, E>(
 	build_parachain_context: P,
 	para_id: ParaId,
 	exit: E,
 	key: Arc<ed25519::Pair>,
-	args: I,
 	version: VersionInfo,
 ) -> polkadot_cli::error::Result<()> where
 	P: BuildParachainContext + Send + 'static,
@@ -442,11 +441,9 @@ pub fn run_collator<P, E, I, ArgT>(
 	<<P::ParachainContext as ParachainContext>::ProduceCandidate as IntoFuture>::Future: Send + 'static,
 	E: IntoFuture<Item=(), Error=()>,
 	E::Future: Send + Clone + Sync + 'static,
-	I: IntoIterator<Item=ArgT>,
-	ArgT: Into<std::ffi::OsString> + Clone,
 {
 	let node_logic = CollationNode { build_parachain_context, exit: exit.into_future(), para_id, key };
-	polkadot_cli::run(args, node_logic, version)
+	polkadot_cli::run(node_logic, version)
 }
 
 #[cfg(test)]