Geometry Nodes: use Still mode by default in Bake node

Currently, the geometry nodes modifier always creates a time dependency
if there is a bake animation node, even if there is no bake. Changing this is
not entirely trivial, because it is only known during evaluation if there is baked
data. Making `Still` the default works around that issue in many cases where
the Bake node is in a node group asset that does not depend on time.

Furthermore, it's nice to have the "cheaper" version of the node by default,
which is baking a single frame, instead of baking everything.

Pull Request: https://projects.blender.org/blender/blender/pulls/117999

source/blender/modifiers/intern/MOD_nodes.cc

@@ -407,6 +407,7 @@ static void update_bakes_from_node_group(NodesModifierData &nmd)
       new_bake.id = id;
       new_bake.frame_start = 1;
       new_bake.frame_end = 100;
+      new_bake.bake_mode = NODES_MODIFIER_BAKE_MODE_STILL;
     }
   }