Implement posix app loading (#643)

- Added POSIX desktop support for SDK builds, application packaging, and integration testing.
- Added POSIX filesystem partitions and improved application path handling.
- Added simulator support for loading and running applications dynamically.
- Improved simulator task stack handling and display startup reliability.
- Improved simulator display scaling, resizing, high-DPI support, and pointer accuracy.
- Fixed LVGL timers and input polling on POSIX. (fixes simulator with Linux on some Intel graphics platforms)
- Standardized data paths across platforms.
- Logging now works via separate task: this allows apps to write to log without it affecting their stdout (for apps that output text as relevant date for other apps, like the File Selection app)
- Fixes for app stdio

Modules/app-module/source/scheduler.cpp

@@ -199,12 +199,19 @@ void app_task_main(void* context) {
     check(pvTaskGetThreadLocalStoragePointer(nullptr, APP_INSTANCE_ID_THREAD_SLOT_INDEX) == nullptr);
     vTaskSetThreadLocalStoragePointer(nullptr, APP_INSTANCE_ID_THREAD_SLOT_INDEX, reinterpret_cast<void*>(static_cast<uintptr_t>(ctx->app_instance_id)));
 
+    // Debug logging so it's invisible by default
+    // When logging happens, it can distort the application stdout, which breaks apps that use
+    // stdout to output important information, such as the file selection dialog app.
     LOG_I(TAG, "[instance %lu] Task started", ctx->app_instance_id);
 
     set_state(ctx->app_instance_id, APP_INSTANCE_STATE_ACTIVE);
 
     int32_t result = ctx->loader->run(ctx->runtime, ctx->app_instance_id, ctx->argc, ctx->argv);
 
+    // The platform might buffer stdout (e.g. esp-idf with newlib)
+    // Do a manual flush to ensure data has been written:
+    fflush(stdout);
+
     vTaskSetThreadLocalStoragePointer(nullptr, APP_INSTANCE_ID_THREAD_SLOT_INDEX, nullptr);
 
     ctx->loader->unload(ctx->runtime);