Add "include-what-you-use" to CI

Currently our builds can take an age with the smallest of change.

Probably we need to do some tree shaking and improve inputs/dependencies between build targets - im guessing esp in the test code

It seems we dont currently check for used includes (not 100% but that seems to be the case)

Perhaps we can add https://github.com/include-what-you-use/include-what-you-use at least to get the signal if not to fix immediately