Reason of deletion prompt when deleting job listings

WP Job Manager could provide a prompt whenever a job listing is deleted, asking for the reason of deletion such as Position already filled or Job Listings no longer exist.

First requested in 4125962-zen

No file or test is named. Start by locating the WordPress admin job-listing deletion entry point and tracing the existing deletion flow. Done should include a deletion prompt that asks for a reason, including examples such as a filled position or unavailable listings, with the selected reason handled as part of the deletion workflow.

Written by the indexing model from the issue text.