[vk,swapchain] vsync: Changed Immediate fallback from (FIFO) to (Mailbox, then FIFO) (#3746)

Just discovered that stock adreno drivers on a730 had no Immediate VSync mode available, and it was falling back to FIFO, which causes a lot of response delay in Unity games.

But if someone chose Immediate, it prefers low latency above buffering, so Mailbox is his friend, and FIFO is his nemesis.

So i just changed Immediate to fall back to Mailbox first, and only if Mailbox is not available either it falls back to FIFO:

Immediate -> Mailbox -> FIFO;
Mailbox -> FIFO;
FIFO Relaxed -> FIFO.

Reviewed-on: https://git.eden-emu.dev/eden-emu/eden/pulls/3746
Reviewed-by: crueter <crueter@eden-emu.dev>
Reviewed-by: MaranBr <maranbr@eden-emu.dev>
Co-authored-by: xbzk <xbzk@eden-emu.dev>
Co-committed-by: xbzk <xbzk@eden-emu.dev>

src/video_core/renderer_vulkan/vk_swapchain.cpp

@@ -65,8 +65,10 @@ static VkPresentModeKHR ChooseSwapPresentMode(bool has_imm, bool has_mailbox,
             return mode;
         }
     }();
+    if (setting == Settings::VSyncMode::Immediate && !has_imm) {
+        setting = Settings::VSyncMode::Mailbox;
+    }
     if ((setting == Settings::VSyncMode::Mailbox && !has_mailbox) ||
-        (setting == Settings::VSyncMode::Immediate && !has_imm) ||
         (setting == Settings::VSyncMode::FifoRelaxed && !has_fifo_relaxed)) {
         setting = Settings::VSyncMode::Fifo;
     }