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

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

src/libslic3r/Print.cpp

@@ -314,6 +314,7 @@ bool Print::invalidate_state_by_config_options(const ConfigOptionResolver & /* n
             //|| opt_key == "resolution"
             //BBS: when enable arc fitting, we must re-generate perimeter
             || opt_key == "enable_arc_fitting"
+            || opt_key == "print_order"
             || opt_key == "wall_sequence") {
             osteps.emplace_back(posPerimeters);
             osteps.emplace_back(posEstimateCurledExtrusions);