Reject excessively large FTP control replies (#2434)

Reject excessively large FTP control replies (#2434)

When parsing FTP control replies, `Ftp::Client::parseControlReply()`
stores individual lines in the `ctrl.message` wordlist. The stored
values are later combined, appended, encoded, and/or converted to String
objects, exposing the results to `String::SizeMax_` limitations. Recent
commit 46f3f80 already ensures `reply_header_max_size` limits for
control replies. This change adds checks for cases where
`reply_header_max_size` configuration exceeds the recommended maximum
value. It also protects any sensitive worldlist-manipulating code that
might become reachable before `reply_header_max_size` limit is checked.

Excessively large FTP control replies now lead to ERR_FTP_FAILURE.

This is a Measurement Factory project.