Fix base-path handling in key insert (#7775)

This fixes the handling of base-path when using `key insert`. Before
the base-path wasn't setup correctly, as done when starting a node. This
resulted in putting the keys into the wrong directory. This pr fixes
this by creating the correct base-path/config dir for the keystore.
Besides that it also removes the insert command from `subkey` as it
doesn't make that much sense. If requested, we could bring it back later.

substrate/client/service/src/config.rs

@@ -263,6 +263,13 @@ impl BasePath {
 			BasePath::Permanenent(path) => path.as_path(),
 		}
 	}
+
+	/// Returns the configuration directory inside this base path.
+	///
+	/// The path looks like `$base_path/chains/$chain_id`
+	pub fn config_dir(&self, chain_id: &str) -> PathBuf {
+		self.path().join("chains").join(chain_id)
+	}
 }
 
 impl std::convert::From<PathBuf> for BasePath {