fix(418): Target temp not restored after filament runout

[m-abs]

Add gcode variables similar to what PAUSE macro uses, to restore target temperature after loading and resuming after filament runout.

Fixes #418

[halfmanbear]

Thank you for raising this. I think the correct fix would be;

[filament_switch_sensor filament_sensor]
pause_on_runout: True
insert_gcode:
  M117 Insert Detected
runout_gcode:
  M117 Runout Detected
  SET_GCODE_VARIABLE MACRO=LOAD_FILAMENT VARIABLE=prev_temp VALUE={printer["gcode_macro RESUME"].etemp|int}
  SET_GCODE_VARIABLE MACRO=UNLOAD_FILAMENT VARIABLE=prev_temp VALUE={printer["gcode_macro RESUME"].etemp|int}
  UNLOAD_FILAMENT
event_delay: 3.0
pause_delay: 1.0
switch_pin: PA12

I've updated the PR code to reflect this. Could you please test