Optimize memory usage of InputEvent lookup.

Move the declaration of look up map to cpp file from header file to
avoid duplicate copies.

Bug: 165527068
Bug: 165398580
Bug: 165035349

Test: atest libinput_tests, atest inputflinger_tests
adb shell showmap <system_server pid> | grep input
Check libinput.so and libinput_reader.so size to be 300 and 372KB.

Change-Id: Ia80200b7889f16ce576637d746e64641f3f2a094