Make it possible to restart kwin_wayland from a command line argument

A recent patch made it possible to restart KWin when it crashes, this opens the possibility to do it for development purposes. So far it could be done using killall -9 kwin_wayland. This patch embraces this functionality under --replace so it's a bit more documented and under its own semantics. It also changes so that the crash counter gets reset when we kill it as it shouldn't be seen as an actual crash.