Move KeyCharacterMap from RefBase to shared_ptr.

Move KeyCharacterMap from RefBase and make it shared_ptr in it's owner
class like EventHub and InputDeviceInfo. When loaded from file, KeyCharacterMap
as shared_ptr is stored in both InputDeviceInfo and EventHub device.

Bug: 160010896
Test: atest inputflinger, atest libinput_tests
Change-Id: Ib3c489c3e87e04d68e4681994e430e43aa46164b