[xnnpack][on-device] executor class (#88778)
# Executor Class
Executor object used to wrap our xnn_runtime object. The ideal flow of this object looks as such:
```
executor.set_inputs(vector<tensor> inputs, vector<tensor> outputs)
executor.forward()
```
This will likely be returned by our delegate compile and given over to execute in order to run inference using the xnn runtime
##### Executorch Considerations
```
#include <ATen/Functions.h>
#include <ATen/Utils.h>
```
These Aten functions are included in order to use at::Tensor when setting the inputs, this will change when used for Executorch because we will be switching from at::Tensor to whatever tensor abstraction is used for ET. Seems like they have the same call for `.data_ptr<float>()`, so realistically all logic here will be the same.
ATen/Utils is used for TORCH_CHECK. We will switch to ET_CHECK_MESSAGE for executorch.
Differential Revision: [D40733121](https://our.internmc.facebook.com/intern/diff/D40733121/)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/88778
Approved by: https://github.com/digantdesai
