feat(printer): add cooling filter support flag and expose its toggle

cooling_filter_enabled existed as a config option but was shown nowhere,
and there was no capability flag to gate it. The cooling filter and air
filtration are alternative accessories sharing the same duct, so a
printer declares one or the other.

- new hidden printer capability flag support_cooling_filter
- "Use cooling filter" toggle in the Accessory group, shown only when
  the printer supports it; the air-filtration toggle hides in that case
  (no vendor restriction: third-party printers keep air filtration)
- explicit defaults (0) in the common machine base
- H2C declares support_cooling_filter=1 instead of support_air_filtration;
  its start-gcode already carries the cooling-filter conditional, so the
  toggle is functional. On H2C this drops the two exhaust-fan lines that
  air filtration emitted for ABS-class filaments, matching the printer's
  actual duct accessory; H2C is new on this branch so no existing user
  output changes.

Printers without the flag keep exactly the previous accessory UI and
g-code.

src/libslic3r/Preset.cpp

@@ -1390,7 +1390,7 @@ static std::vector<std::string> s_Preset_printer_options {
     "default_print_profile", "inherits",
     "silent_mode",
     "scan_first_layer", "enable_power_loss_recovery", "wrapping_detection_layers", "wrapping_exclude_area", "machine_load_filament_time", "machine_unload_filament_time", "machine_tool_change_time", "time_cost", "machine_pause_gcode", "template_custom_gcode",
-    "nozzle_type", "nozzle_hrc","auxiliary_fan", "fan_direction", "nozzle_volume","upward_compatible_machine", "z_hop_types", "travel_slope", "retract_lift_enforce","support_chamber_temp_control","support_air_filtration","cooling_filter_enabled","printer_structure","farthest_point_timelapse",
+    "nozzle_type", "nozzle_hrc","auxiliary_fan", "fan_direction", "nozzle_volume","upward_compatible_machine", "z_hop_types", "travel_slope", "retract_lift_enforce","support_chamber_temp_control","support_air_filtration","support_cooling_filter","cooling_filter_enabled","printer_structure","farthest_point_timelapse",
     "best_object_pos", "head_wrap_detect_zone",
     "host_type", "print_host", "printhost_apikey", "flashforge_serial_number", "bbl_use_printhost", "printer_agent",
     "print_host_webui",