Ported Polar, Turbo and FFT to Highway

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
• [] New functions adhere to RAL's naming scheme
• [] Contribution conforms to RAL's directory structure
• [] Documentation updated
• [] "Unreleased" section of the Changelog updated
• [] clang-format and clang-tidy run and changes included (C/C++ code)
• [] flake8 run and changes included (Python code)
• [] cmake-format run and changes included (CMake code)
• [] Tests added or updated
• [] Tests pass when run with AddressSanitizer
• [] Benchmarks added or updated

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