[3.11] gh-85984: Utilize new "winsize" functions from termios in pty tests. (GH-101831) (#104652)

Utilize new functions termios.tcgetwinsize() and termios.tcsetwinsize in test_pty.py.

(cherry picked from commit da2fb9264315dc30ac3012b4dbf5ba76d3f34433)

Co-authored-by: Soumendra Ganguly <67527439+8vasu@users.noreply.github.com>
Co-authored-by: Gregory P. Smith <greg@krypto.org>