Combine brims option (Prusa style brims) (#12343)

* Union ex brims

Revert "Union ex brims"

This reverts commit bbc9a39faf318dc2df093eb2bdcebf19a4162fe9.

Update Brim.cpp

* dont repeat paths

* Update Brim.cpp

* multimaterial brim independiente

* Normal brim if is by object

* fix print order

* cleaning 1

* cleaning 2

* Normal brim if multimaterial on first layer

* fix artifact

* combine_brim optional

refactoring

* refactoring gcode.cpp

* refactoring brim.cpp

Update Brim.cpp

* Remove multimaterial first-layer check for brims

Stop detecting extruders used on the first layer and remove the is_multimaterial_first_layer guard. Simplify can_combine_brims to only consider combine_brims and whether printing is ByObject, allowing brims to be combined across extruders unless printing by object or combine_brims is disabled. Cleans up unused code and simplifies brim-generation conditions.

* Remove material specification from unified brim comment

* Update PrintConfig.cpp

src/slic3r/GUI/Plater.cpp

@@ -4809,7 +4809,7 @@ Plater::priv::priv(Plater *q, MainFrame *main_frame)
         "extruder_clearance_radius",
         "extruder_clearance_height_to_lid", "extruder_clearance_height_to_rod",
 		"nozzle_height", "skirt_type", "skirt_loops", "skirt_speed","min_skirt_length", "skirt_distance", "skirt_start_angle",
-        "brim_width", "brim_object_gap", "brim_use_efc_outline", "brim_type", "nozzle_diameter", "single_extruder_multi_material", "preferred_orientation",
+        "brim_width", "brim_object_gap", "brim_use_efc_outline", "combine_brims", "brim_type", "nozzle_diameter", "single_extruder_multi_material", "preferred_orientation",
         "enable_prime_tower", "wipe_tower_x", "wipe_tower_y", "prime_tower_width", "prime_tower_brim_width", "prime_tower_skip_points", "prime_tower_enable_framework",
         "prime_tower_infill_gap", "prime_volume",
         "extruder_colour", "filament_colour", "filament_type", "material_colour", "printable_height", "extruder_printable_height", "printer_model", "printer_technology",