logic: reimplemented task system to abort ast visiting

* reimplemented interrupting TaskParseCxx by adding a listener for the MessageInterruptTask and returning a failure status code on update. This cancels the parent sequence task which results in the indexed items not getting inserted into the persistent storage
* removed the capability for interrupting from TaskScheduler
* changed task system to be closer to the standard behavior tree implementation
* changed task system to accommodate the 3 status return types: Running, Success and Failure
* made TaskGroupSequential fail once a member task fails
* made TaskGroupParallel fail once a member task fails
* split TaskParse... into one task for indexing and one task for injecting
* added TaskRunner that handles updating and resetting the managed task
* fixed numbers that are shown as parsed file count in indexing ui
* fixed deadlock that originated from interaction between TaskScheduler and MessageQueue (one thread wanted to destroy a message listener on a task while the other one wanted to send as message as a task)

src/lib/utility/file/FileRegister.cpp

@@ -230,5 +230,17 @@ size_t FileRegister::getSourceFilesCount() const
 
 size_t FileRegister::getParsedSourceFilesCount() const
 {
-	return getSourceFilesCount() - getUnparsedSourceFilePaths().size();
+	std::lock_guard<std::mutex> lock(m_sourceFileMutex);
+
+	size_t count = 0;
+
+	for (std::pair<FilePath, ParseState>&& p : m_sourceFilePaths)
+	{
+		if (p.second == STATE_PARSED)
+		{
+			count++;
+		}
+	}
+
+	return count;
 }