Refactor EventHubTests to use UinputDevice

EventHubTests uses uinput to emulate input devices. We refactor the
system calls into a untility file UinputDevice.h so it can be reused for
other integration tests.

Test: atest inputflinger_tests
Change-Id: If6b1b94b14c0bc71193cbc69ce1239a01990559b
4 files changed