Add checksum to emoji-compat metadata

This CL updates createfont.py script. It calculates a checksum from
source emoji font, flat buffer schema and emoji metadata. Finally it
embeds this checksum into font metadata.

Test: ./gradlew support-emoji:connectedAndroidCheck

Bug: 62024362
Change-Id: I161daa8aa9af5a767eb7d26af94e391be5187320
(cherry picked from commit ddd072a17bcb3a87600d72230132aed850a9e8ad)
4 files changed