Returns a Page out of the Page System without reading it.
The method calling this method will remove the page and will start reading it outside of any
locks. This method could also replace the current file by a new file, and that process is done
through acquiring a writeLock on currentPageLock.
Observation: This method is used internally as part of the regular depage process, but
externally is used only on tests, and that's why this method is part of the Testable Interface