Simple IPC for external control (#3345)

* add simple IPC protocol

to allow communication via stdin/stdout

* ipc: add PATCH_MEMORY command

enables patches & cheates

src/core/ipc/ipc.h

@@ -0,0 +1,39 @@
+//  SPDX-FileCopyrightText: Copyright 2024 shadPS4 Emulator Project
+//  SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "common/singleton.h"
+
+#include <semaphore>
+#include <thread>
+
+class IPC {
+    bool enabled{false};
+    std::jthread input_thread{};
+
+    std::binary_semaphore run_semaphore{0};
+    std::binary_semaphore start_semaphore{0};
+
+public:
+    static IPC& Instance() {
+        return *Common::Singleton<IPC>::Instance();
+    }
+
+    void Init();
+
+    operator bool() const {
+        return enabled;
+    }
+
+    [[nodiscard]] bool IsEnabled() const {
+        return enabled;
+    }
+
+    void WaitForStart() {
+        start_semaphore.acquire();
+    }
+
+private:
+    [[noreturn]] void InputLoop();
+};