tests: provide FTP directory contents in the test file

tests: provide FTP directory contents in the test file

Instead of providing a fixed single synthetic response in the test
server itself. To allow us to better use *different* directory listings
in different test cases. In this change, most listings remain the same
as before.

The wildcard match tests still use synthetic responses but we should fix
that as well.

Updated numerous test cases to use this.

Closes #14295