Proposal: Given a root wiki page, display a list of subpages for the given root wiki page on the deletion form and allow to check/uncheck some/all of them to be deleted with the root wiki page as well.

Rationale: Currently deleting a page with a large number of subpages is very tedious given that you need to open each and every subpage and perform an individual deletion. While this can be achieved via scripting or a bot, this is not affordable for all wiki administrators out there, so we should make MediaWiki to support this option by default.

Notes: probably deletions should happen in batches, not all at the same time, to avoid stressing the databases too much.

Similar to T32893: Add option to delete all redirects pointing to a page. However this task aims to be more selective, considering that this one requests that MediaWiki let you choose what to delete and what not, not delete all subpages in a all-or-nothing fashion.