Remove the ad-hoc cooling override now that COOL handles it natively

TempControllerBase.cooling/set_cooling() forced y=0 in advance of a
Sud ramp-down step; redundant now that the FSM's own COOL state
detects and handles a negative diff itself. Removed from the
controller, SudTask's anticipatory detection (and the Step message's
now-unused "Cooling" field), and demo_sud.py's mirror of it.

gui: the "Cool down" status-bar indicator now reflects the
controller's actual State ("States.COOL") via the TempCtrl channel,
rather than Sud's removed anticipatory flag - renamed
sud_cooling/set_sud_cooling to tc_cooling/set_tc_cooling to match.

components/pid/temp_controller_base.py

@@ -45,14 +45,6 @@ class TempControllerBase(APid):
 		self.pid_rate.set_params(params['Heat'])
 		self.pid_cool.set_params(params['Cool'])
 		self.is_startup = True
-		# Explicit override for a ramp step whose target is below the
-		# current temperature: forces y to 0 immediately rather than
-		# waiting for the FSM's own (slower, hysteresis-based) COOL
-		# transition, as soon as the caller (SudTask) knows the step needs
-		# to passively cool down. Mostly superseded by the COOL state
-		# below for a heat-only actuator (both end up clamped to 0
-		# power) - kept for the immediate, decided-in-advance response.
-		self.cooling = False
 		# Master on/off switch: while disabled, the FSM is held in IDLE and
 		# the controller tries not to drive the heater at all (output
 		# forced to 0) - off by default, enabled either by the user
@@ -91,9 +83,6 @@ class TempControllerBase(APid):
 	def set_heatrate_soll(self, value):
 		self.heatrate_soll_set = value
 
-	def set_cooling(self, value):
-		self.cooling = value
-
 	def set_enabled(self, value):
 		self.enabled = value
 
@@ -150,7 +139,7 @@ class TempControllerBase(APid):
 		self.pid_rate.process(heatrate_err, -self.heatrate_ist)
 		self.pid_cool.process(heatrate_err, -self.heatrate_ist)
 
-		if self.state == States.IDLE or self.cooling:
+		if self.state == States.IDLE:
 			self.y = 0
 		elif self.state == States.COOL:
 			self.y = self.pid_cool.get_y()