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.
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 is supported. You have to have it installed.
5. nnet_utils has some unmodified code, that I probably should not have included. Just Dense and activations have been modified (plus some of the general).

Type of change

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

Tests

It has only been tested with the jet-tagging code from the tutorial, with backend=oneAPI

Test Configuration:

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.