[libinput] Add middle mouse button emulation support

Wraps libinput
libinput_device_config_middle_emulation_is_available
libinput_device_config_middle_emulation_set_enabled
libinput_device_config_middle_emulation_get_enabled
libinput_device_config_middle_emulation_get_default_enabled

Differential Revision: https://phabricator.kde.org/D3187
BUG: 371756
FIXED-IN: 5.8.4