[vk] unify VkSurfaceKHR with Android and the rest of platforms; remove technically incorrect nullptr() ctor for handles (#2971)

Removes some odd #ifdef-ing that just can use a shrimple opaque type.

Also removes nullptr() ctor'ing for vulkan handles and such; it's not incorrect per se like how `void *p = 0;` isn't incorrect, just that, y'know, any static analyzer will go "woah". Also there isn't any guarantee that handles `sizeof(Handle) == sizeof(void*)` so may as well :)

Signed-off-by: lizzie lizzie@eden-emu.dev

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/2971
Reviewed-by: CamilleLaVey <camillelavey99@gmail.com>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Co-authored-by: lizzie <lizzie@eden-emu.dev>
Co-committed-by: lizzie <lizzie@eden-emu.dev>

src/video_core/vulkan_common/vulkan.h

@@ -1,4 +1,4 @@
-// SPDX-FileCopyrightText: Copyright 2025 Eden Emulator Project
+// SPDX-FileCopyrightText: Copyright 2026 Eden Emulator Project
 // SPDX-License-Identifier: GPL-3.0-or-later
 
 // SPDX-FileCopyrightText: Copyright 2023 yuzu Emulator Project
@@ -40,3 +40,6 @@
 #undef False
 #undef None
 #undef True
+
+// "Catch-all" handle for both Android and.. the rest of platforms
+struct VkSurfaceKHR_T;