[3.15] gh-87451: Apply CVE-2021-4189 PASV fix to ftplib.ftpcp() (GH-149648) (#149792)

[3.15] gh-87451: Apply CVE-2021-4189 PASV fix to ftplib.ftpcp() (GH-149648) (#149792)

gh-87451: Apply CVE-2021-4189 PASV fix to ftplib.ftpcp() (GH-149648)

ftpcp() called parse227() directly and passed the source server's
self-reported PASV IPv4 address to the target server's PORT command,
bypassing the CVE-2021-4189 fix that was applied only to FTP.makepasv().
A malicious source FTP server could use this to redirect the target
server's data connection to an arbitrary host:port (SSRF).

ftpcp() now uses the source server's actual peer address, honoring the
existing trust_server_pasv_ipv4_address opt-out, the same as makepasv().

Thanks to Qi Ding at Aurascape AI for the report. (GHSA-w8c5-q2xf-gf7c)
(cherry picked from commit eac4fe3b2c77693790a5ef7dfab127c1fee81bf9)

Co-authored-by: Gregory P. Smith <68491+gpshead@users.noreply.github.com>