* [Simulator][FIFOBufferDevice][FilteredTextBuffer]
* Fix issues with dynamic memory allocation on Linux (closes#6119);
* Fix occasional issue with long lines getting partially repeated in output;
* Fixes filter buffer getting overwhelmed with some very verbose Horus startups (observed on Linux);
* Adjust buffer max. size settings to int type (to match QByteArray size type);
* Re-implement QIODevice bytesAvailable() and canReadLine() for efficiency;
* Remove some unnecessary vars, other minor optimizations, cosmetics.
* [Simulator] Slightly optimize DebugOutput::processBytesReceived() by using QByteArray directly.
