SystemServer: Propagate errors

This patch also includes some changes in the way that the environment
and arguments are passed to `exec`. It was needed to fit the signature
of `Core::System::exec`. That's beneficial though, as we are now doing
`String` manipulation in a fallible environment, so we can propagate
more errors.

Userland/Services/SystemServer/Service.h

@@ -21,8 +21,8 @@ public:
     ~Service();
 
     bool is_enabled() const;
-    void activate();
-    void did_exit(int exit_code);
+    ErrorOr<void> activate();
+    ErrorOr<void> did_exit(int exit_code);
 
     static Service* find_by_pid(pid_t);
 
@@ -32,7 +32,7 @@ public:
 private:
     Service(Core::ConfigFile const&, StringView name);
 
-    void spawn(int socket_fd = -1);
+    ErrorOr<void> spawn(int socket_fd = -1);
 
     ErrorOr<void> determine_account(int fd);
 
@@ -50,7 +50,7 @@ private:
     // Path to the executable. By default this is /bin/{m_name}.
     DeprecatedString m_executable_path;
     // Extra arguments, starting from argv[1], to pass when exec'ing.
-    Vector<DeprecatedString> m_extra_arguments;
+    DeprecatedString m_extra_arguments;
     // File path to open as stdio fds.
     DeprecatedString m_stdio_file_path;
     int m_priority { 1 };
@@ -71,7 +71,7 @@ private:
     // Whether several instances of this service can run at once.
     bool m_multi_instance { false };
     // Environment variables to pass to the service.
-    Vector<DeprecatedString> m_environment;
+    DeprecatedString m_environment;
     // Socket descriptors for this service.
     Vector<SocketDescriptor> m_sockets;
 
@@ -91,5 +91,5 @@ private:
     ErrorOr<void> setup_socket(SocketDescriptor&);
     ErrorOr<void> setup_sockets();
     void setup_notifier();
-    void handle_socket_connection();
+    ErrorOr<void> handle_socket_connection();
 };