Cleanup and improvements (#194)

- Lots of changes for migrating C code to C++
- Improved `Lockable` in several ways like adding `withLock()` (+ tests)
- Improved `Semaphore` a bit for improved readability, and also added some tests
- Upgrade Linux machine in GitHub Actions so that we can compile with a newer GCC
- Simplification of WiFi connection
- Updated funding options
- (and more)

Tactility/Private/app/wificonnect/State.h

@@ -20,9 +20,6 @@ public:
     void setConnectionError(bool error);
     bool hasConnectionError() const;
 
-    const service::wifi::settings::WifiApSettings& lockApSettings();
-    void unlockApSettings();
-
     void setApSettings(const service::wifi::settings::WifiApSettings* newSettings);
 
     void setConnecting(bool isConnecting);