* native time measurer for determining n_times
* added nano second unit, unit tests pass there

PICK ME UP:
* Integration tests failing
* running fast_functions seems to break as well

…nersion like we want

* RepeatedMeasurement to unit test it and not pollute general
runner with this very specific code for runtime measurements
that's only relevant on Windows these days it seems
* Hooks code in its own module to not pollute and reuse from both
place
* made `measure` public on the runner... not 100% happy with this
but putting it into even another module seems like an overhead
now.
* temporarily duplicated `main_function` code