Affected functions (all on Linux/Mac):
- `RouterLinux::flushDns` was not reloading the DNS manager.
- `Utils::processIsRunning` was always saying that the process
is not running when `fullFlag` was set to `false`.
- `Utils::killProcessByName` was not killing anything.
* used a Qt6 ported version of SortFilterProxyModel
* used an updated Qt6 compatible version of QXZing
* added a flag to windows linker to avoid WinMain problem of MSVCRTD
* renamed utils.cpp to utilities.cpp for avoiding confusion with the same file name in SortFilterProxyModel