feat(orient): auto-orient the largest overhang toward the cooling fan

New printer option fan_direction (undefine/left/right/both, default
undefine) declares which side the auxiliary part-cooling airflow comes
from. When set and the printer has an auxiliary fan, auto-orient adds a
yaw rotation so the dominant overhang area faces the airflow, and newly
added primitive shapes are pre-oriented the same way (except the Cube,
whose axis-aligned bounding box the pressure-advance pattern calibration
depends on).

- FanDirection enum + fan_direction printer option (Accessory group,
  enabled only with auxiliary_fan)
- orient engine: weighted overhang areas per candidate, yaw-direction
  search, vertical rotation applied on top of the primary orientation;
  the cooling weights are taken from the candidate actually chosen,
  including the flat-bottom tie-break
- orient_for_cooling() for primitive placement
- set fan_direction=left on H2C/H2D/H2D Pro/X1/X1E/P1S 0.4 profiles
  (X1C/H2S/P2S/X2D/Qidi X-Max 4 already carried the key, which now
  takes effect)

With fan_direction unset or no auxiliary fan the vertical rotation stays
identity and auto-orient results are unchanged; slicing and g-code are
never affected.

src/slic3r/GUI/Tab.cpp

@@ -4956,6 +4956,7 @@ void TabPrinter::build_fff()
         optgroup->append_single_option_line("nozzle_type", "printer_basic_information_accessory#nozzle-type");
         optgroup->append_single_option_line("nozzle_hrc", "printer_basic_information_accessory#nozzle-hrc");
         optgroup->append_single_option_line("auxiliary_fan", "printer_basic_information_accessory#auxiliary-part-cooling-fan");
+        optgroup->append_single_option_line("fan_direction");
         optgroup->append_single_option_line("support_chamber_temp_control", "printer_basic_information_accessory#support-controlling-chamber-temperature");
         optgroup->append_single_option_line("support_air_filtration", "printer_basic_information_accessory#support-air-filtration");
 
@@ -5892,6 +5893,8 @@ void TabPrinter::toggle_options()
 
         const bool support_parallel_printheads = printer_cfg.opt_bool("support_parallel_printheads");
         toggle_line("parallel_printheads_count", support_parallel_printheads);
+
+        toggle_line("fan_direction", m_config->opt_bool("auxiliary_fan"));
     }