CLI improvements & fixes (#4812)

These are a few changes I missed during the refactoring.

1. Initialization issue and boilerplate

    Most importantly: part of the `Configuration` initialization was done in `sc_cli::init`. This means the user can not benefit from this initialization boilerplate if they have multiple `Configuration` since `sc_cli::init` can only be called once.

2. Boilerplate for `VersionInfo` and `Configuration`

    I'm also answering to the critic of @bkchr on the initialization using version: https://github.com/paritytech/substrate/pull/4692/files/bea809d4c14a2ede953227ac885e3b3f9771c548#r372047238 This will allow initializing a `Configuration` and provide the version by default.

3. Loading the `chain_spec` explicitly

    In the past it was done automatically but in some cases we want to delay this. I moved the code to `Configuration.load_spec()` so it can be called later on. `chain_spec` can also be written directly to the `Configuration` without using this `load_spec` helper.

4. [deleted]

5. Fixing issue that prevents the user to override the port

    In the refactoring I introduced a bug by mistake that could potentially prevent the CLI user to override the ports if defaults where provided for these ports (only on cumulus).

6. Change task_executor from Box to Arc

    This is useful for cumulus where we have 2 nodes with 2 separate Configuration that need to spawn tasks to the same runtime.

7. Renamed TasksExecutorRequired to TaskExecutor

    For consistency.

This is related to https://github.com/paritytech/cumulus/issues/24

This is the continuation (and hopefully the end of) #4692

substrate/bin/node/cli/tests/running_the_node_and_interrupt.rs

@@ -0,0 +1,58 @@
+// Copyright 2020 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+use assert_cmd::cargo::cargo_bin;
+use std::convert::TryInto;
+use std::process::{Child, Command, ExitStatus};
+use std::thread::sleep;
+use std::time::Duration;
+
+#[test]
+#[cfg(unix)]
+fn running_the_node_works_and_can_be_interrupted() {
+	use nix::sys::signal::{kill, Signal::{self, SIGINT, SIGTERM}};
+	use nix::unistd::Pid;
+
+	fn wait_for(child: &mut Child, secs: usize) -> Option<ExitStatus> {
+		for _ in 0..secs {
+			match child.try_wait().unwrap() {
+				Some(status) => return Some(status),
+				None => sleep(Duration::from_secs(1)),
+			}
+		}
+		eprintln!("Took to long to exit. Killing...");
+		let _ = child.kill();
+		child.wait().unwrap();
+
+		None
+	}
+
+	fn run_command_and_kill(signal: Signal) {
+		let mut cmd = Command::new(cargo_bin("substrate")).spawn().unwrap();
+		sleep(Duration::from_secs(30));
+		assert!(cmd.try_wait().unwrap().is_none(), "the process should still be running");
+		kill(Pid::from_raw(cmd.id().try_into().unwrap()), signal).unwrap();
+		assert_eq!(
+			wait_for(&mut cmd, 30).map(|x| x.success()),
+			Some(true),
+			"the pocess must exit gracefully after signal {}",
+			signal,
+		);
+	}
+
+	run_command_and_kill(SIGINT);
+	run_command_and_kill(SIGTERM);
+}