Cleanup: Add function to check a curve's spline types

The need for this has come up a few times.

source/blender/blenkernel/BKE_spline.hh

@@ -543,6 +543,7 @@ struct CurveEval {
 
   blender::Span<SplinePtr> splines() const;
   blender::MutableSpan<SplinePtr> splines();
+  bool has_spline_with_type(const Spline::Type type) const;
 
   void resize(const int size);
   void add_spline(SplinePtr spline);

source/blender/blenkernel/intern/curve_eval.cc

@@ -48,6 +48,22 @@ blender::MutableSpan<SplinePtr> CurveEval::splines()
   return splines_;
 }
 
+/**
+ * \return True if the curve contains a spline with the given type.
+ *
+ * \note If you are looping over all of the splines in the same scope anyway,
+ * it's better to avoid calling this function, in case there are many splines.
+ */
+bool CurveEval::has_spline_with_type(const Spline::Type type) const
+{
+  for (const SplinePtr &spline : this->splines()) {
+    if (spline->type() == type) {
+      return true;
+    }
+  }
+  return false;
+}
+
 void CurveEval::resize(const int size)
 {
   splines_.resize(size);

source/blender/blenkernel/intern/geometry_component_curve.cc

@@ -854,17 +854,9 @@ class PositionAttributeProvider final : public BuiltinPointAttributeProvider<flo
       return {};
     }
 
-    bool curve_has_bezier_spline = false;
-    for (SplinePtr &spline : curve->splines()) {
-      if (spline->type() == Spline::Type::Bezier) {
-        curve_has_bezier_spline = true;
-        break;
-      }
-    }
-
     /* Use the regular position virtual array when there aren't any Bezier splines
      * to avoid the overhead of checking the spline type for every point. */
-    if (!curve_has_bezier_spline) {
+    if (!curve->has_spline_with_type(Spline::Type::Bezier)) {
       return BuiltinPointAttributeProvider<float3>::try_get_for_write(component);
     }