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/test-parachains/halt/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "halt"
+version = "0.1.0"
+authors = ["Parity Technologies <admin@parity.io>"]
+description = "Test parachain which executes forever"
+edition = "2018"
+build = "build.rs"
+
+[dependencies]
+
+[build-dependencies]
+wasm-builder-runner = { package = "substrate-wasm-builder-runner", version = "1.0.2" }
+
+[features]
+default = [ "std" ]
+no_std = []
+std = []