Beginnings of the oneAPI backend

[jmitrevs]

Description

This is the beginning of the oneAPI backend, and is just included here for easier sharing and discussion. It is not ready for merging. Currently only io_parallel Dense and activation layers are supported.

Some things to discuss are:

1. The usage of std::array for sending data on the pipe, and also between layers. It is generally easier to send std::array than a struct containing C arrays, I believe. (Note, std::array is passed as nnet::array, so it's possible to change in one place the array definition.)
2. The addition of oneapi_types.py instead of adding the types in fpga_types.py. I think we want to split fpga_types.py. Otherwise catapult types will soon also come there.
3. This uses cmake to build the libraries and testbench. The setup is based on the examples in https://github.com/oneapi-src/oneAPI-samples
4. Currently only oneAPI 2024.0.0 or later is supported. You have to have it installed.

There is more information on the status at the following link:
https://www.icloud.com/keynote/0e6hRDG4E4PazKCJkJ-ur3yTg#oneAPIDev

Type of change

• New feature (non-breaking change which adds functionality)

Tests

oneAPI has been added as a backend in many tests.

Checklist

• I have read the guidelines for contributing.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have installed and run pre-commit on the files I edited or added.
• I have added tests that prove my fix is effective or that my feature works.

[jmitrevs]

I think the optimizer to clone outputs needs updates to work with oneAPI.

[jmitrevs]

Actually, I believe I was wrong about the optimizer to clone outputs. It was migrated. I added a clone outputs test, and I removed what looks to be the redundant test_stream_multi_clone.py