[ET] Add RuntimeContext to ET Aten mode (#96084)
Summary:
In ATen mode, we add the RuntimeContext arg, so we have something like
```
TORCH_API inline at::Tensor & gelu_outf(torch::executor::RuntimeContext & context, const at::Tensor & self, c10::string_view approximate, at::Tensor & out) {
return at::gelu_outf(self, approximate, out);
}
```
and user can use `<namespace like aten>::gelu_outf` and we will automatically dispatch the registered function in aten kernel using `at::gelu_outf` (dispatched by ATen/Functions.h header)
In optimized kernel tests, we can now automatically handle between aten kernel and optimized kernel.
The implication is that the test must depend on the correctness of codegen; an error in codegen can break the kernel tests.
Test Plan: CI
Differential Revision: D43777848
Pull Request resolved: https://github.com/pytorch/pytorch/pull/96084
Approved by: https://github.com/larryliu0820
