Free up space taken up by deleted projects

Carryover proposal item (4) from the MVC released in #24866 (closed)

Problem to solve

While projects are being delete, there is a period in time that they still occupy space on the disk. Administrators need a rapid mechanism to free up space when necessary.

Proposal

There should be the option to "delete all removed projects now" as well, which should be useful when you want to free space from disk.

Documentation