## Description

Please find an MR for the following Highway ported feature sets
- Polar
- Updated Turbo decoder
- FFT (generated FFTs)

Additional changes
- Update copyright notices
- Replaced submodule with FetchContent command
- Minor updates to use either the upstreamed code in Highway or `hwy_extra_ops.h`

## Checklist

* [] [Contribution meets RAL's licence terms](https://gitlab.arm.com/networking/ral/-/blob/main/CONTRIBUTING.md#user-content-licensing-information)
* [] [New functions adhere to RAL's naming scheme](https://gitlab.arm.com/networking/ral/-/blob/main/CONTRIBUTING.md#user-content-function-naming)
* [] [Contribution conforms to RAL's directory structure](https://gitlab.arm.com/networking/ral/-/blob/main/CONTRIBUTING.md#user-content-directory-structure)
* [] [Documentation updated](https://gitlab.arm.com/networking/ral/-/blob/main/CONTRIBUTING.md#user-content-documentation)
* [] ["Unreleased" section of the Changelog updated](https://gitlab.arm.com/networking/ral/-/blob/main/CHANGELOG.md#unreleased)
* [] [`clang-format` and `clang-tidy` run and changes included (C/C++ code)](https://gitlab.arm.com/networking/ral/-/blob/main/CONTRIBUTING.md#user-content-cc-code-style)
* [] [`flake8` run and changes included (Python code)](https://gitlab.arm.com/networking/ral/-/blob/main/CONTRIBUTING.md#user-content-python-code-style)
* [] [`cmake-format` run and changes included (CMake code)](https://gitlab.arm.com/networking/ral/-/blob/main/CONTRIBUTING.md#user-content-cmake-code-style)
* [] [Tests added or updated](https://gitlab.arm.com/networking/ral/-/blob/main/CONTRIBUTING.md#user-content-writing-tests)
* [] [Tests pass when run with AddressSanitizer](https://gitlab.arm.com/networking/ral/-/blob/main/CONTRIBUTING.md?ref_type=heads#user-content-testing-with-addresssanitizer)
* [] [Benchmarks added or updated](https://gitlab.arm.com/networking/ral/-/blob/main/CONTRIBUTING.md#user-content-writing-benchmarks)

For any items that are not checked, please provide details.