service/sockets: Implement network services for new firmware versions

This commit implements various network services required for newer firmware
versions. Key changes include:

- Add bsd:nu service for firmware 15.0.0+ with proper event handling
- Add bsdcfg implementation with complete interface declarations
- Add dns:priv and ethc (c/i) services
- Register all new services in the service manager
- Extend BSD implementation with additional socket operations
- Remove room_network instance variable in favor of system.GetRoomNetwork()
- Fix kernel event creation by using ServiceContext in all appropriate places
- Update build system to include new source files

Signed-off-by: Zephyron <zephyron@citron-emu.org>

src/core/hle/service/sockets/ethc.h

@@ -0,0 +1,26 @@
+// SPDX-FileCopyrightText: Copyright 2025 citron Emulator Project
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#pragma once
+
+#include "core/hle/service/service.h"
+
+namespace Core {
+class System;
+}
+
+namespace Service::Sockets {
+
+class ETHC_C final : public ServiceFramework<ETHC_C> {
+public:
+    explicit ETHC_C(Core::System& system_);
+    ~ETHC_C() override;
+};
+
+class ETHC_I final : public ServiceFramework<ETHC_I> {
+public:
+    explicit ETHC_I(Core::System& system_);
+    ~ETHC_I() override;
+};
+
+} // namespace Service::Sockets