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-posix-module/tests/fixtures/fixture_app.cpp

@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: Apache-2.0
+#include <app/scheduler.h>
+
+#include <cstdint>
+
+// Deliberately not linked against app-module: app_scheduler_current_app_id() stays an undefined
+// symbol in this .so, resolved at dlopen() time against the loading process's own copy. Proves
+// app-posix-module's loader lets a loaded app call straight back into Tactility without linking
+// its own copy of it.
+extern "C" int32_t main(int, char*[]) {
+    return static_cast<int32_t>(app_scheduler_current_app_id());
+}