Geometry Nodes: Add named attribute nodes behind experimental flag

This commit adds three nodes:
- `Remove Attribute`: Removes an attribute with the given name
- `Named Attribute`: A field input node
- `Store Named Attribute`: Puts results of a field in a named attribute

They are added behind a new experimental feature flag, because further
development of attribute search and name dependency visualization will
happen as separate steps.

Ref T91742

Differential Revision: https://developer.blender.org/D12685

1 files changed, 2 insertions, 1 deletions

diff --git a/source/blender/makesdna/DNA_userdef_types.h b/source/blender/makesdna/DNA_userdef_types.h
index 80a107e4bae..5784d437048 100644
--- a/source/blender/makesdna/DNA_userdef_types.h
+++ b/source/blender/makesdna/DNA_userdef_types.h
@@ -650,7 +650,8 @@ typedef struct UserDef_Experimental {
   char use_sculpt_tools_tilt;
   char use_extended_asset_browser;
   char use_override_templates;
-  char _pad[2];
+  char use_named_attribute_nodes;
+  char _pad[1];
   /** `makesdna` does not allow empty structs. */
 } UserDef_Experimental;