Fix DisplayControl classpath

Use the full system server classpath to load DisplayControl, so that
turning the screen off on Android 14+ does not crash on certain devices.

Refs #4544 comment <https://github.com/Genymobile/scrcpy/issues/4544#issuecomment-2526999714>
Fixes #4544 <https://github.com/Genymobile/scrcpy/issues/4544>
Fixes #5274 <https://github.com/Genymobile/scrcpy/issues/5274>

Signed-off-by: Romain Vimont <rom@rom1v.com>