Refactor SDL/FreeRTOS implementation to support macOS simulator properly (#653)

- Run SDL from main() and place FreeRTOS in separate thread. This fixes macOS support.
- Updated GitHub Actions to publish macOS simulator build for testing, updated amd64 to x86_64 for consistent naming.

Devices/simulator/Source/Main.cpp

@@ -10,13 +10,13 @@ constexpr auto* TAG = "FreeRTOS";
 
 namespace simulator {
 
-MainFunction mainFunction = nullptr;
+static MainFunction mainFunction = nullptr;
 
 void setMain(MainFunction newMainFunction) {
     mainFunction = newMainFunction;
 }
 
-static void freertosMainTask(void* parameter) {
+static void freertosMainTask(void*) {
     LOG_I(TAG, "starting app_main()");
     assert(simulator::mainFunction);
     mainFunction();