Add options to list more than just the first page of scheduled posts

For sake of simplicity, listing scheduled posts currently only shows the first page. It should be possible to list any page and set the page size via command line arguments.

Start by locating the command-line handling for listing scheduled posts and the code that requests the first page. Trace how the current page size is fixed, then verify that page and page-size arguments can select different results and that the requested list is displayed.

Written by the indexing model from the issue text.