[Feature] Enabled gap fill algorithm for all solid fill types (#3412)

* ENH: Enabled gap fill algorithm for all solid fill types

* Made gap fill an option & refactored code into its own method

* Code comment updates

* Converted gap fill to enum and control filter out gap fill in the UI

* Update label for consistency

* Spelling mistake

src/libslic3r/PrintConfig.hpp

@@ -152,10 +152,17 @@ enum SeamPosition {
     spNearest, spAligned, spRear, spRandom
 };
 
+//Orca
 enum InternalBridgeFilter {
     ibfDisabled, ibfLimited, ibfNofilter
 };
 
+//Orca
+enum GapFillTarget {
+     gftEverywhere, gftTopBottom, gftNowhere
+ };
+
+
 enum LiftType {
     NormalLift,
     SpiralLift,
@@ -789,6 +796,7 @@ PRINT_CONFIG_CLASS_DEFINE(
     ((ConfigOptionPercent,            tree_support_top_rate))
     ((ConfigOptionFloat,              tree_support_branch_diameter_organic))
     ((ConfigOptionFloat,              tree_support_branch_angle_organic))
+    ((ConfigOptionEnum<GapFillTarget>,gap_fill_target))
     ((ConfigOptionFloat,              min_length_factor))
 
     // Move all acceleration and jerk settings to object