xclient.send_request() should just take a Request object and handle
to_bytes with the right byte order. This avoids typos/copy-paste errors
in tests when the byte order changes between tests.
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2216>
This test was missing SetClientVersion(2) so the reply was a the old 0.x
protocol (and the 36 byte GetModeLine reply). Update so it runs for both
versions now.
Fixes: acbc46e708 ("pyxtest: add tests for the byteswapping patches")
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2213>