Add setting to specialise the wall transitioning angle

Similar to the previous setting Wall Transition Length, but this determines how fast lines come together, which can be faster than the Wall Transition Length.

Contributes to issue CURA-7686.

resources/definitions/fdmprinter.def.json

@@ -1080,6 +1080,18 @@
                     "maximum_value_warning": "2 * line_width",
                     "maximum_value": "min_bead_width * 3 * math.pi"
                 },
+                "wall_transition_angle":
+                {
+                    "label": "Wall Transition Angle",
+                    "description": "When transitioning between different numbers of walls as the part becomes thinner, two adjacent walls will join together at this angle. This can make the walls come together faster than what the Wall Transition Length indicates, filling the space better.",
+                    "type": "float",
+                    "unit": "°",
+                    "default_value": 30,
+                    "minimum_value": "1",
+                    "minimum_value_warning": "15",
+                    "maximum_value_warning": "50",
+                    "maximum_value": "59"
+                },
                 "wall_0_wipe_dist":
                 {
                     "label": "Outer Wall Wipe Distance",