Use InputChannel::create

InputChannel no longer allows direct creation, because it may be
invalid, depending on the data provided. Force the users to check the
result of the creation by only allowing the use of static creators
::read and ::create.

Bug: none
Test: atest libinput_tests inputflinger_tests
Change-Id: Ieb746036798cf673ceb63cbc1d59a9be7e5cc05a