ENH: apply fan speed immediately after changing layer

What: As title. The original code is always apply
at the end of last object of last layer, whichi is before
layer change

Why: the fan spped will be skipped if the last object is
skipped. So we must move the layer time fan speed setting
after changing layer, where is common gcode block and does
not belong to any object.

Signed-off-by: salt.wei <salt.wei@bambulab.com>
Change-Id: I442f80e00778b524576210b451f81dd15e25e14c

src/libslic3r/GCode/CoolingBuffer.hpp

@@ -59,6 +59,9 @@ private:
     bool                        m_cooling_logic_proportional = false;
     //BBS: current fan speed
     int                         m_current_fan_speed;
+    //BBS:
+    bool                        m_set_fan_changing_layer = false;
+    bool                        m_set_addition_fan_changing_layer = false;
 };
 
 }