[NNAPI] Use code generation to better support list input/output (#54697)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/54697
Previously, models being converted to NNAPI were expected to take inputs
as separate arguments, but the generated NNAPI model could only take
multiple inputs as a list. Now the generated model always takes inputs
(single or multiple) as separate tensor arguments.
Previously, models being converted to NNAPI were expected to return
outputs as a single tensor or tuple of tensors, but the generated NNAPI
model would return multiple outputs as a list. Now the generated model
returns a tuple as well (or single tensor).
Internally, we decied what output format to use (single tensor or tuple)
based on the conversion process, rather than by running the model.
Test Plan: Unit test
Reviewed By: axitkhurana
Differential Revision: D27536790
Pulled By: dreiss
fbshipit-source-id: c0f93c85d450757e568985947cc2f32043795859
