[3.11] gh-114241: Fix and improve the ftplib CLI (GH-114242) (GH-114405)

* Fix writing the retrieved binary file to stdout.
* Add a newline after writing warnings to stderr.
* Fix a TypeError if the netrc file doesn't contain a host/default entry.
* Improve the usage message.
(cherry picked from commit 42d72b23dd1ee0e100ee47aca64fc1e1bbe576c9)

Co-authored-by: Serhiy Storchaka <storchaka@gmail.com>