[exir][delegate] torch.ops.call_delegate (#92562)
Summary:
Followup diffs to integrate this op into the other parts of the delegate workflow.
The unittest results in the following graph:
```
graph():
%x_1 : [#users=1] = placeholder[target=x_1]
%y_1 : [#users=1] = placeholder[target=y_1]
%lowered_module_0 : [#users=1] = get_attr[target=lowered_module_0]
%call_delegate : [#users=1] = call_function[target=torch.ops.call_delegate](args = (%lowered_module_0, forward, %x_1, %y_1), kwargs = {})
return call_delegate
```
Test Plan: buck2 run //executorch/exir/tests:delegate -- -r "test_call_delegate"
Differential Revision: D42329287
Pull Request resolved: https://github.com/pytorch/pytorch/pull/92562
Approved by: https://github.com/voznesenskym
