Animation: minor speedup when accessing id properties

This is fundamentally quadratic code until #140907 is implemented. However, the
old approach that didn't use `StringRef` was a few percent faster because it
didn't have to call `strlen` as often. So this brings back a little bit of
performance in cases like #140706.

Pull Request: https://projects.blender.org/blender/blender/pulls/144012

source/blender/blenkernel/BKE_idprop.hh

@@ -191,6 +191,13 @@ void IDP_FreeFromGroup(IDProperty *group, IDProperty *prop) ATTR_NONNULL();
 IDProperty *IDP_GetPropertyFromGroup(const IDProperty *prop,
                                      blender::StringRef name) ATTR_WARN_UNUSED_RESULT
     ATTR_NONNULL();
+/**
+ * This is a slightly more efficient version of the function above in the when there are lots of
+ * properties. It can be faster because it avoids computing the length of everything that the
+ * string is compared to. Also see #140706.
+ */
+IDProperty *IDP_GetPropertyFromGroup(const IDProperty *prop,
+                                     const char *name) ATTR_WARN_UNUSED_RESULT ATTR_NONNULL();
 /**
  * Same as #IDP_GetPropertyFromGroup but ensure the `type` matches.
  */

source/blender/blenkernel/intern/idprop.cc

@@ -769,6 +769,13 @@ IDProperty *IDP_GetPropertyFromGroup(const IDProperty *prop, const blender::Stri
   return BLI_listbase_find<IDProperty>(prop->data.group,
                                        [&](const IDProperty &elem) { return elem.name == name; });
 }
+
+IDProperty *IDP_GetPropertyFromGroup(const IDProperty *prop, const char *name)
+{
+  BLI_assert(prop->type == IDP_GROUP);
+  return (IDProperty *)BLI_findstring(&prop->data.group, name, offsetof(IDProperty, name));
+}
+
 IDProperty *IDP_GetPropertyTypeFromGroup(const IDProperty *prop,
                                          const blender::StringRef name,
                                          const char type)