Check whether the child process is alive during the bridge construction

[isidentical]

isolate/src/isolate/backends/connections/ipc/_base.py

Lines 116 to 122 in 6587d96

	# TODO(fix): this might hang if the agent process crashes before it can
	# connect to the controller bridge.
	self.log(
	f"Awaiting agent process of {isolated_process.pid}"
	" to establish a connection."
	)
	established_connection = stack.enter_context(controller_service.accept())