Move KeyCharacterMap from RefBase to shared_ptr.

Move KeyCharacterMap from RefBase and make it shared_ptr in EventHub
device when loaded from file.
A shared_ptr of KeyCharacterMap is returned by EventHub getKeyCharacterMap
to be shared in InputdeviceInfo.
Remove extra KeyCharacterMap in EventHub to save memory sapce.

Bug: 160010896
Test: atest inputflinger, atest libinput_tests

Change-Id: Ibb317ea0684e6af6e7a6d808f816fc4a05c7b421