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)

TactilityCore/Source/StringUtils.h

@@ -7,15 +7,6 @@
 
 namespace tt::string {
 
-/**
- * Find the last occurrence of a character.
- * @param[in] text the text to search in
- * @param[in] from_index the index to search from (searching from right to left)
- * @param[in] find the character to search for
- * @return the index of the found character, or -1 if none found
- */
-int findLastIndex(const char* text, size_t from_index, char find);
-
 /**
  * Given a filesystem path as input, try and get the parent path.
  * @param[in] path input path