WindowServer: Rename WSEvent to WSMessage.

Also do the same for WSMessageLoop and WSMessageReceiver. More to come.

WindowServer/WSMessageLoop.h

@@ -0,0 +1,45 @@
+#pragma once
+
+#include "WSMessage.h"
+#include <AK/Lock.h>
+#include <AK/OwnPtr.h>
+#include <AK/Vector.h>
+
+class WSMessageReceiver;
+class Process;
+
+class WSMessageLoop {
+public:
+    WSMessageLoop();
+    ~WSMessageLoop();
+
+    int exec();
+
+    void post_event(WSMessageReceiver* receiver, OwnPtr<WSMessage>&&);
+
+    static WSMessageLoop& the();
+
+    static void initialize();
+
+    bool running() const { return m_running; }
+    Process& server_process() { return *m_server_process; }
+
+private:
+    void wait_for_event();
+    void drain_mouse();
+    void drain_keyboard();
+
+    Lock m_lock;
+
+    struct QueuedEvent {
+        WSMessageReceiver* receiver { nullptr };
+        OwnPtr<WSMessage> event;
+    };
+    Vector<QueuedEvent> m_queued_events;
+
+    Process* m_server_process { nullptr };
+    bool m_running { false };
+
+    int m_keyboard_fd { -1 };
+    int m_mouse_fd { -1 };
+};