QOL: add repeated normalize/denormalize functions to InputValue

[pastaq]

In our source and target device implementations, it is normal for us to re-implement the same [de]normalize_[un]signed_value functions. These are all called from a driver specific normalize_[axis|trigger]_value function. As the code is identical in every instance, we can reduce the amount of code we need to copy/paste if we include these translators into src/input/event/value.rs and import it where needed.