[3/N] Nnapi Backend Delegate Preprocess: Basic OSS Test (#61594)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/61594
### Summary:
Added a unit test for the Nnapi delegate's preprocess() function. The
function was previously tested locally, but now a basic test is
added for OSS.
See https://github.com/pytorch/pytorch/pull/61499 for preprocess
implementation. See D29647123 for local testing.
**TODO:**
Add more comprehensive tests.
Add tests for model execution, after the Nnapi delegate's initialization
and execution is implemented T91991928.
**CMakeLists.txt:**
Added a library for the Nnapi delegate
- Explicit linking of torch_python is necessary for the Nnapi delegate's use of pybind
**test_backends.py:**
Added a test for lowering to Nnapi
- Based off https://github.com/pytorch/pytorch/blob/master/test/test_nnapi.py
- Only differences are the loading of the nnapi backend library and the need to change dtype from float64 to float32
### Test Plan:
Running `python test/test_jit.py TestBackendsWithCompiler -v` succeeds. Also saved and examined the model file locally.
Test Plan: Imported from OSS
Reviewed By: iseeyuan
Differential Revision: D29687143
fbshipit-source-id: 9ba9e57f7f856e5ac15e13527f6178d613b32802
