fix: assign descriptive node names to lifted Constant nodes

Use f'initializer_{value.name}' as the node name for Constant nodes
created by lift_initializers_to_constants. This follows the same
likely-unique heuristic as the builder's own naming scheme
(f'{op_type}_node_{count}') and makes lifted constants easily
identifiable in the graph.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Signed-off-by: G Ramalingam <grama@microsoft.com>

Author: gramalingam

onnxscript/_internal/builder.py

@@ -112,6 +112,7 @@ def lift_initializers_to_constants(graph: ir.Graph) -> None:
             attributes=[ir.Attr("value", ir.AttributeType.TENSOR, tensor)],
             outputs=[value],
             version=opset_version,
+            name=f"initializer_{value.name}",
         )
         graph.initializers.pop(value.name)
         new_nodes.append(node)