• Disable statement handler if we don't connect to a debugging client at start up (unless coverage mode is enabled, in which case it needs to remain enabled)
• Enable it again if later on we connect to a debugging client
• There are a couple of places where we also need to temporarily enable it when we set do_connect_to_client to true. The code that acts upon this flag is called from the statement handler, so we need to enable it so that it can try to connect. If it does not connect, it will be disabled again

This provides a performance gain between 1% and 10% depending on the type of application that we are running. See some benchmarking results here: https://github.com/carlos-granados/xdebug/actions/runs/21043818969