Update Emoji.java to use ICU

Overrides have been added to update the data to Emoji 5.0, since our
version of ICU only supports Emoji 4.0.

Test: CTS tests continue to pass.
Bug: 27365282
Bug: 30874706
Change-Id: I7c791e1e75ea3510b36f258c1e1c7184051d6d3a