GPencil: Consider extrude point as last

Before, when extrude a point, the extruded point is considered as the first point of the stroke, but this was not logic.

Now, the extrude point is considered as last.

Related to T79313

source/blender/editors/gpencil/gpencil_edit.c

@@ -94,6 +94,8 @@
 /** \name Stroke Edit Mode Management
  * \{ */
 
+static void gpencil_flip_stroke(bGPDstroke *gps);
+
 /* poll callback for all stroke editing operators */
 static bool gpencil_stroke_edit_poll(bContext *C)
 {
@@ -1126,6 +1128,11 @@ static void gpencil_add_move_points(bGPDframe *gpf, bGPDstroke *gps)
       pt->flag |= GP_SPOINT_SELECT;
     }
 
+    /* Flip stroke if it was only one point to consider extrude point as last point. */
+    if (gps->totpoints == 2) {
+      gpencil_flip_stroke(gps);
+    }
+
     /* Calc geometry data. */
     BKE_gpencil_stroke_geometry_update(gps);