Allow specifying print order within each layer (#3685)

* Allow reordering objects regardless of print seq

* Add option to control the layer print order

* Sort object by their order in object list instead of id

* Show print order when print order is the same as the object list

* Ensure the print order when print order is same as object list

* Update option name

---------

Co-authored-by: SoftFever <softfeverever@gmail.com>

src/libslic3r/PrintConfig.hpp

@@ -106,6 +106,13 @@ enum class PrintSequence {
     Count,
 };
 
+enum class PrintOrder
+{
+    Default,
+    AsObjectList,
+    Count,
+};
+
 enum class SlicingMode
 {
     // Regular, applying ClipperLib::pftNonZero rule when creating ExPolygons.
@@ -1101,6 +1108,7 @@ PRINT_CONFIG_CLASS_DERIVED_DEFINE(
     ((ConfigOptionInts,               overhang_fan_speed))
     ((ConfigOptionEnumsGeneric,       overhang_fan_threshold))
     ((ConfigOptionEnum<PrintSequence>,print_sequence))
+    ((ConfigOptionEnum<PrintOrder>,   print_order))
     ((ConfigOptionInts,               first_layer_print_sequence))
     ((ConfigOptionBools,              slow_down_for_layer_cooling))
     ((ConfigOptionInts,               close_fan_the_first_x_layers))