SkipPoolCreation: preserve host UP and DOWN lifecycle processing

[dkropachev]

Problem

SkipPoolCreation returns before all host UP and DOWN processing:

python-driver/cassandra/cluster.py

Lines 1917 to 1922 in b666e5c

	def on_up(self, host):
	"""
	Intended for internal use only.
	"""
	if self.is_shutdown or self.allow_control_connection_query_fallback == ControlConnectionQueryFallback.SkipPoolCreation:
	return

python-driver/cassandra/cluster.py

Lines 2025 to 2030 in b666e5c

	def on_down(self, host, is_host_addition, expect_host_to_be_down=False):
	"""
	Intended for internal use only.
	"""
	if self.is_shutdown or self.allow_control_connection_query_fallback == ControlConnectionQueryFallback.SkipPoolCreation:
	return

This prevents host status updates, listener notifications, and control-connection failover:

python-driver/cassandra/cluster.py

Lines 2013 to 2023 in b666e5c

	@run_in_executor
	def on_down_potentially_blocking(self, host, is_host_addition):
	self.profile_manager.on_down(host)
	self.control_connection.on_down(host)
	for session in tuple(self.sessions):
	session.on_down(host)
	for listener in self.listeners:
	listener.on_down(host)
	self._start_reconnector(host, is_host_addition)

Pool creation is already disabled in the session paths:

python-driver/cassandra/cluster.py

Lines 3330 to 3339 in b666e5c

	def add_or_renew_pool(self, host, is_host_addition):
	"""
	For internal use only.
	"""
	if self.cluster.allow_control_connection_query_fallback is ControlConnectionQueryFallback.SkipPoolCreation:
	return None
	distance = self._profile_manager.distance(host)
	if distance == HostDistance.IGNORED:
	return None

Expected behavior

Continue normal host lifecycle processing in SkipPoolCreation mode while keeping node-pool creation disabled.