[inductor] Fix constant folder (#166655)

Fixes https://fb.workplace.com/groups/1028545332188949/permalink/1351999569843522/ where the resulting graph of constant folder uses a sym node which has been created later. Graph diff: https://www.internalfb.com/intern/diffing/?paste_number=2014609054

Before:
```
    %full_65 : [num_users=1] = call_function[target=torch.ops.aten.full.default](args = ([%sym_size_int_47, 768], 1), kwargs = {dtype: torch.int64, layout: torch.strided, device: cuda:0, pin_memory: False})
    %select_18 : [num_users=1] = call_function[target=torch.ops.aten.select.int](args = (%full_65, 1, 0), kwargs = {})
    %mul_2792 : [num_users=1] = call_function[target=torch.ops.aten.mul.Tensor](args = (%select_18, 0), kwargs = {})
    %embedding_4 : [num_users=1] = call_function[target=torch.ops.aten.embedding.default](args = (%_uv__surface_embeddings_weight, %mul_2792), kwargs = {})
```

After:
```
    %full_65 : [num_users=1] = call_function[target=torch.ops.aten.full.default](args = ([%sym_size_int_47, 768], 1), kwargs = {dtype: torch.int64, layout: torch.strided, device: cuda:0, pin_memory: False})
    %full_default_1 : [num_users=1] = call_function[target=torch.ops.aten.full.default](args = ([%sym_size_int_150], 0), kwargs = {dtype: torch.int64, layout: torch.strided, device: cuda:0, pin_memory: False})
    %embedding_4 : [num_users=1] = call_function[target=torch.ops.aten.embedding.default](args = (%_uv__surface_embeddings_weight, %full_default_1), kwargs = {})
    ...
    %sym_size_int_150 : [num_users=7] = call_function[target=torch.ops.aten.sym_size.int](args = (%view_193, 0), kwargs = {})
```

I couldn't figure out a small repro for this :/

Pull Request resolved: #166655
Approved by: https://github.com/eellison

Author: angelayi

torch/_inductor/fx_passes/joint_graph.py

@@ -227,7 +227,8 @@ def __init__(self, gm, skip_constructors=False) -> None:
         self.symint_nodes = _SymHashingDict()
         for n in self.module.graph.nodes:  # type: ignore[union-attr]
             if "val" in n.meta and isinstance(n.meta["val"], torch.SymInt):
-                self.symint_nodes[n.meta["val"]] = n
+                if n.meta["val"] not in self.symint_nodes:
+                    self.symint_nodes[n.meta["val"]] = n
 
         # reference from torch/_funtorch/partitioners.py:get_default_op_list
         self.view_op_packets = [