[Refactor] Move Default page size and test type to lib/backendtypes package

There are a few methods that we could benefit from moving the `backend` package to the shared `lib/backendtypes` package.

Such as getPageSizeOrDefault for page size

This is because we are having some of the workers call some existing code and they don't have access to some of the same helpers since they aren't in the lib package. Moving those there would help out.