Rewrite host GPU abstraction

- Don't have to repeat the same thing for 4 renderers.
 - Add native Metal renderer.

src/duckstation-nogui/cocoa_nogui_platform.h

@@ -0,0 +1,74 @@
+// SPDX-FileCopyrightText: 2019-2023 Connor McLaughlin <stenzek@gmail.com>
+// SPDX-License-Identifier: (GPL-3.0 OR CC-BY-NC-ND-4.0)
+
+#pragma once
+
+#include <AppKit/AppKit.h>
+#include <Cocoa/Cocoa.h>
+
+#ifndef __OBJC__
+#error This file needs to be compiled with Objective C++.
+#endif
+
+#if __has_feature(objc_arc)
+#error ARC should not be enabled.
+#endif
+
+#include "nogui_platform.h"
+
+#include <atomic>
+
+@interface CocoaNoGUIView : NSView<NSWindowDelegate>
+- (BOOL)acceptsFirstResponder;
+- (BOOL)canBecomeKeyView;
+- (void)mouseDown:(NSEvent *)event;
+- (void)rightMouseDown:(NSEvent *)event;
+- (void)otherMouseDown:(NSEvent *)event;
+- (void)mouseUp:(NSEvent *)event;
+- (void)rightMouseUp:(NSEvent *)event;
+- (void)otherMouseUp:(NSEvent *)event;
+- (void)mouseMoved:(NSEvent *)event;
+- (void)keyDown:(NSEvent *)event;
+- (void)keyUp:(NSEvent *)event;
+- (void)windowDidEndLiveResize:(NSNotification *)notif;
+@end
+
+class CocoaNoGUIPlatform : public NoGUIPlatform
+{
+public:
+  CocoaNoGUIPlatform();
+  ~CocoaNoGUIPlatform();
+
+  bool Initialize();
+
+  void ReportError(const std::string_view& title, const std::string_view& message) override;
+  bool ConfirmMessage(const std::string_view& title, const std::string_view& message) override;
+
+  void SetDefaultConfig(SettingsInterface& si) override;
+
+  bool CreatePlatformWindow(std::string title) override;
+  bool HasPlatformWindow() const override;
+  void DestroyPlatformWindow() override;
+  std::optional<WindowInfo> GetPlatformWindowInfo() override;
+  void SetPlatformWindowTitle(std::string title) override;
+
+  std::optional<u32> ConvertHostKeyboardStringToCode(const std::string_view& str) override;
+  std::optional<std::string> ConvertHostKeyboardCodeToString(u32 code) override;
+
+  void RunMessageLoop() override;
+  void ExecuteInMessageLoop(std::function<void()> func) override;
+  void QuitMessageLoop() override;
+
+  void SetFullscreen(bool enabled) override;
+
+  bool RequestRenderWindowSize(s32 new_window_width, s32 new_window_height) override;
+
+  bool OpenURL(const std::string_view& url) override;
+  bool CopyTextToClipboard(const std::string_view& text) override;
+
+private:
+  NSWindow* m_window = nil;
+  float m_window_scale = 1.0f;
+
+  std::atomic_bool m_fullscreen{false};
+};