[export] Add effect token to export (#121424)
Following the creation of effect tokens (https://github.com/pytorch/pytorch/pull/120296), we want to now add support for these tokens in export because the calling/returning convention has changed. The inputs are now `(tokens, params, buffers, constants, user_inputs)` and the outputs are `(tokens, buffer_mutations, user_mutations, user_outputs)`. The graph looks something like:
```
graph():
%arg0_1 : [num_users=1] = placeholder[target=arg0_1]
%attr : [num_users=2] = placeholder[target=attr]
%arg1_1 : [num_users=2] = placeholder[target=arg1_1]
%with_effects : [num_users=2] = call_function[target=torch._higher_order_ops.effects.with_effects](args = (%arg0_1, _TorchScriptTesting.takes_foo.default, %attr, %arg1_1), kwargs = {})
%getitem : [num_users=1] = call_function[target=operator.getitem](args = (%with_effects, 0), kwargs = {})
%getitem_1 : [num_users=1] = call_function[target=operator.getitem](args = (%with_effects, 1), kwargs = {})
%with_effects_1 : [num_users=2] = call_function[target=torch._higher_order_ops.effects.with_effects](args = (%getitem, _TorchScriptTesting.takes_foo.default, %attr, %getitem_1), kwargs = {})
%getitem_2 : [num_users=1] = call_function[target=operator.getitem](args = (%with_effects_1, 0), kwargs = {})
%getitem_3 : [num_users=1] = call_function[target=operator.getitem](args = (%with_effects_1, 1), kwargs = {})
%add : [num_users=1] = call_function[target=torch.ops.aten.add.Tensor](args = (%arg1_1, %getitem_3), kwargs = {})
return (getitem_2, add)
```
During unlifting, we will first remove the tokens and with_effect calls using the `remove_effect_tokens` pass. (cc @SherlockNoMad on the pass to remove tokens). This is so that this won't change the calling conventions when retracing. The graph after unlifting looks something like:
```
graph():
%attr_1 : [num_users=2] = get_attr[target=attr]
%arg1_1 : [num_users=2] = placeholder[target=arg1_1]
%takes_foo_default_1 : [num_users=1] = call_function[target=torch.ops._TorchScriptTesting.takes_foo.default](args = (%attr_1, %arg1_1), kwargs = {})
%takes_foo_default : [num_users=1] = call_function[target=torch.ops._TorchScriptTesting.takes_foo.default](args = (%attr_1, %takes_foo_default_1), kwargs = {})
%add : [num_users=1] = call_function[target=torch.ops.aten.add.Tensor](args = (%arg1_1, %takes_foo_default), kwargs = {})
return (add,)
```
Serialization support will be added in a followup.
Note: tokens only affect custom ops that take in ScriptObjects, not ScriptObject methods yet.
Differential Revision: [D54639390](https://our.internmc.facebook.com/intern/diff/D54639390)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/121424
Approved by: https://github.com/tugsbayasgalan
