[libinput] Add scroll method configuration support

Wraps libinput
libinput_device_config_scroll_get_methods
libinput_device_config_scroll_get_default_method
libinput_device_config_scroll_set_method
libinput_device_config_scroll_get_method
libinput_device_config_scroll_set_button
libinput_device_config_scroll_get_button
libinput_device_config_scroll_get_default_button

Subscribers: kwin
Tags: #kwin
Differential Revision: https://phabricator.kde.org/D3194
BUG: 371803
FIXED-IN: 5.8.4