Ensure asset serving is portable

Fixes #3094

* Ensure fingerprinting works on Windows
* Removed some tests from versioned assets because these are now explicitly tested with a generated reverse router in the routes-compiler-plugin scripted tests.
* Made a few stylistic changes (mainly because IntelliJ was marking it as a warning).
Looks like this should be `.drop(base.size + 1` now, given the changes?