CLI API refactoring and improvement (#4692)

It changes the way we extended the CLI functionalities of substrate to allow more flexibility. (If this was not clear, here is another version: it changes the `sc_cli` API to allow more flexibility).

This touches a few important things:
 - the startup of the async task with tokei:
    This was in node and node-template and I moved it to substrate. The idea is to have 1 time the code that handles unix signals (SIGTERM and SIGINT) properly. It is however possible to make this more generic to wait for a future instead and provide only a helper for the basic handling of SIGTERM and SIGINT.
 - increased the version of structopt and tokei
 - no more use of structopt internal's API
 - less use of generics

Related to #4643 and https://github.com/paritytech/cumulus/pull/42: the implementation of "into_configuration" and "get_config" are similar but with better flexibility so it is now possible in cumulus to have the command-line arguments only of the run command for polkadot if we want

Related to https://github.com/paritytech/cumulus/issues/24 and https://github.com/paritytech/cumulus/issues/34 : it will now be possible to make a configuration struct for polkadot with some overrides of the default parameters much more easily.

substrate/client/service/src/config.rs

@@ -23,13 +23,13 @@ pub use sc_executor::WasmExecutionMethod;
 
 use std::{future::Future, path::{PathBuf, Path}, pin::Pin, net::SocketAddr, sync::Arc};
 pub use sc_transaction_pool::txpool::Options as TransactionPoolOptions;
-use sc_chain_spec::{ChainSpec, RuntimeGenesis, Extension, NoExtension};
+use sc_chain_spec::{ChainSpec, NoExtension};
 use sp_core::crypto::Protected;
 use target_info::Target;
 use sc_telemetry::TelemetryEndpoints;
 
 /// Service configuration.
-pub struct Configuration<C, G, E = NoExtension> {
+pub struct Configuration<G, E = NoExtension> {
 	/// Implementation name
 	pub impl_name: &'static str,
 	/// Implementation version
@@ -39,7 +39,7 @@ pub struct Configuration<C, G, E = NoExtension> {
 	/// Node roles.
 	pub roles: Roles,
 	/// How to spawn background tasks. Mandatory, otherwise creating a `Service` will error.
-	pub tasks_executor: Option<Box<dyn Fn(Pin<Box<dyn Future<Output = ()> + Send>>) + Send>>,
+	pub task_executor: Option<Box<dyn Fn(Pin<Box<dyn Future<Output = ()> + Send>>) + Send>>,
 	/// Extrinsic pool configuration.
 	pub transaction_pool: TransactionPoolOptions,
 	/// Network configuration.
@@ -57,9 +57,7 @@ pub struct Configuration<C, G, E = NoExtension> {
 	/// Pruning settings.
 	pub pruning: PruningMode,
 	/// Chain configuration.
-	pub chain_spec: ChainSpec<G, E>,
-	/// Custom configuration.
-	pub custom: C,
+	pub chain_spec: Option<ChainSpec<G, E>>,
 	/// Node name.
 	pub name: String,
 	/// Wasm execution method.
@@ -146,22 +144,18 @@ pub enum DatabaseConfig {
 	Custom(Arc<dyn KeyValueDB>),
 }
 
-impl<C, G, E> Configuration<C, G, E> where
-	C: Default,
-	G: RuntimeGenesis,
-	E: Extension,
-{
-	/// Create a default config for given chain spec and path to configuration dir
-	pub fn default_with_spec_and_base_path(chain_spec: ChainSpec<G, E>, config_dir: Option<PathBuf>) -> Self {
-		let mut configuration = Configuration {
+impl<G, E> Default for Configuration<G, E> {
+	/// Create a default config
+	fn default() -> Self {
+		let configuration = Configuration {
 			impl_name: "parity-substrate",
 			impl_version: "0.0.0",
 			impl_commit: "",
-			chain_spec,
-			config_dir: config_dir.clone(),
+			chain_spec: None,
+			config_dir: None,
 			name: Default::default(),
 			roles: Roles::FULL,
-			tasks_executor: None,
+			task_executor: None,
 			transaction_pool: Default::default(),
 			network: Default::default(),
 			keystore: KeystoreConfig::None,
@@ -171,7 +165,6 @@ impl<C, G, E> Configuration<C, G, E> where
 			},
 			state_cache_size: Default::default(),
 			state_cache_child_ratio: Default::default(),
-			custom: Default::default(),
 			pruning: PruningMode::default(),
 			wasm_method: WasmExecutionMethod::Interpreted,
 			execution_strategies: Default::default(),
@@ -191,16 +184,13 @@ impl<C, G, E> Configuration<C, G, E> where
 			tracing_targets: Default::default(),
 			tracing_receiver: Default::default(),
 		};
-		configuration.network.boot_nodes = configuration.chain_spec.boot_nodes().to_vec();
-
-		configuration.telemetry_endpoints = configuration.chain_spec.telemetry_endpoints().clone();
 
 		configuration
 	}
 
 }
 
-impl<C, G, E> Configuration<C, G, E> {
+impl<G, E> Configuration<G, E> {
 	/// Returns full version string of this configuration.
 	pub fn full_version(&self) -> String {
 		full_version_from_strs(self.impl_version, self.impl_commit)
@@ -216,11 +206,20 @@ impl<C, G, E> Configuration<C, G, E> {
 	pub fn in_chain_config_dir(&self, sub: &str) -> Option<PathBuf> {
 		self.config_dir.clone().map(|mut path| {
 			path.push("chains");
-			path.push(self.chain_spec.id());
+			path.push(self.expect_chain_spec().id());
 			path.push(sub);
 			path
 		})
 	}
+
+	/// Return a reference to the `ChainSpec` of this `Configuration`.
+	///
+	/// ### Panics
+	///
+	/// This method panic if the `chain_spec` is `None`
+	pub fn expect_chain_spec(&self) -> &ChainSpec<G, E> {
+		self.chain_spec.as_ref().expect("chain_spec must be specified")
+	}
 }
 
 /// Returns platform info