Refactor: Anim, use blender::listbase_to_vector

Add a `const` version of `blender::listbase_to_vector`, and use it in
`animrig::fcurves_for_action_slot()`.

No functional changes.

source/blender/animrig/intern/action_legacy.cc

@@ -5,6 +5,8 @@
 #include "ANIM_action.hh"
 #include "ANIM_action_legacy.hh"
 
+#include "BLI_listbase_wrapper.hh"
+
 #include "BKE_fcurve.hh"
 
 namespace blender::animrig::legacy {
@@ -140,11 +142,7 @@ static Vector<FCurveType *> fcurves_for_action_slot_templated(ActionType &action
   /* Legacy Action. */
   if (action.is_action_legacy()) {
 #endif /* WITH_ANIM_BAKLAVA */
-    Vector<FCurveType *> legacy_fcurves;
-    LISTBASE_FOREACH (FCurveType *, fcurve, &action.curves) {
-      legacy_fcurves.append(fcurve);
-    }
-    return legacy_fcurves;
+    return listbase_to_vector<FCurveType>(action.curves);
 #ifdef WITH_ANIM_BAKLAVA
   }
 

source/blender/blenlib/BLI_listbase_wrapper.hh

@@ -112,4 +112,17 @@ template<typename T> Vector<T *> listbase_to_vector(ListBase &list)
   return vector;
 }
 
+/**
+ * Convert a ListBase to a Vector.
+ */
+template<typename T> Vector<T *> listbase_to_vector(const ListBase &list)
+{
+  Vector<T *> vector;
+
+  for (T *item : ConstListBaseWrapper<T>(list)) {
+    vector.append(item);
+  }
+  return vector;
+}
+
 } /* namespace blender */