[input_reader] Add touchpad and touchscreen interface tests

Add interface testing for the touchpad and touchscreen.
Interface testing catches an existing earlier problem
of doing a double read. It also ensures that the
InputReportPtr is updated correctly.

SCN-1237 #done
TC-319 #done

TESTING: fx run-image-test input_apptests

Change-Id: I214a9720c82018d6d6f50aa4505876dc0b48a49e
3 files changed