Add max_page_size config option

[ripatel-fd]

fdctl/fd_topob is hardcoded to allocate gigantic and huge pages as backing memory for a workspace.

Users should have the option to limit the max page size to 2M or 4K for a few reasons

• Many cloud instances don't support gigantic pages
• Nodes with too high uptime have physical memory fragmentation beyond rescue, and rebooting is not an option

The easiest way to achieve this is probably to add a config option for the max page size, that defaults to 1G