Create inputreader directory

In order to start the work to split InputReader.cpp into multiple files,
we first create a reader directory to hold the source files for
libinputreader.

The affected files are also reformatted with clang-format.

Bug: 140139676
Test: libinputflinger and libinputflinger_tests builds successfully for
  crosshatch

Change-Id: I62b6b873e2a03e61655eb6214183c984306dcfdb