Refactor WebGPU ASYNCIFY to use JSPI

Smaller build size and better performance. Also, link time goes down a lot

Source/Engine/Main/Web/main.cpp

@@ -5,8 +5,33 @@
 #include "Engine/Engine/Engine.h"
 #include <emscripten/emscripten.h>
 
+// Reference: https://github.com/kainino0x/webgpu-cross-platform-demo/blob/f5c69c6fccbb2584c1b6f9e559f9a41a38a9b5ad/main.cpp#L692-L704
+// Reference: https://github.com/kainino0x/webgpu-cross-platform-demo/blob/c26ea3e29ed9f73f9b39bddf7964b482ce3c6964/main.cpp#L737-L758
+#define WEB_LOOP_MODE 2 // 0 - default, 1 - Asyncify, 2 - JSPI
+#if WEB_LOOP_MODE != 0
+// Workaround for JSPI not working in emscripten_set_main_loop. Loosely based on this code:
+// https://github.com/emscripten-core/emscripten/issues/22493#issuecomment-2330275282
+// This code only works with JSPI is enabled.
+typedef bool (*FrameCallback)(); // If callback returns true, continues the loop.
+EM_JS(void, requestAnimationFrameLoopWithJSPI, (FrameCallback callback), {
+#if WEB_LOOP_MODE == 2
+    var callback = WebAssembly.promising(getWasmTableEntry(callback));
+#elif WEB_LOOP_MODE == 1
+    var callback = () = > globalThis['Module']['ccall']("callback", "boolean", [], [], { async: true });
+#endif
+    async function tick() {
+        // Start the frame callback. 'await' means we won't call
+        // requestAnimationFrame again until it completes.
+        var keepLooping = await callback();
+        if (keepLooping) requestAnimationFrame(tick);
+    }
+    requestAnimationFrame(tick);
+    })
+#endif
+
 class PlatformMain
 {
+#if WEB_LOOP_MODE == 0
     static void Loop()
     {
         // Tick engine
@@ -16,11 +41,30 @@ class PlatformMain
         {
             // Exit engine
             Engine::OnExit();
-            emscripten_cancel_main_loop();
-            emscripten_force_exit(Engine::ExitCode);
             return;
         }
     }
+#else
+    static bool Loop()
+    {
+        if (Engine::FatalError != FatalErrorType::None)
+            return false;
+
+        // Tick engine
+        Engine::OnLoop();
+
+        if (Engine::ShouldExit())
+        {
+            // Exit engine
+            Engine::OnExit();
+            emscripten_cancel_main_loop();
+            emscripten_force_exit(Engine::ExitCode);
+            return false;
+        }
+
+        return true;
+    }
+#endif
 
 public:
     static int32 Main()
@@ -31,7 +75,11 @@ public:
             return result;
 
         // Setup main loop to be called by Emscripten
+#if WEB_LOOP_MODE == 0
         emscripten_set_main_loop(Loop, -1, false);
+#else
+        requestAnimationFrameLoopWithJSPI(Loop);
+#endif
         emscripten_set_main_loop_timing(EM_TIMING_RAF, 1); // Run main loop on each animation frame (vsync)
 
         // Run the first loop