Fixes and improvements (#185)

- unPhone improvements related to power and boot (add boot count logging)
- Cleanup of Mutex acquire/release
- Removed `tt_assert()` in favour of `assert()`
- Fix sim build (likely failed due to migration of GitHub Actions to Ubuntu 24.04)

Boards/UnPhone/Source/hal/UnPhoneDisplay.cpp

@@ -56,7 +56,7 @@ bool UnPhoneDisplay::start() {
 }
 
 bool UnPhoneDisplay::stop() {
-    tt_assert(displayHandle != nullptr);
+    assert(displayHandle != nullptr);
 
     lv_display_delete(displayHandle);
     displayHandle = nullptr;