Move GraphicsStatsService native method registration to zygote.

It used to be in system server, but this is for a class in boot
classpath so we can move it to AndroidRuntime.cpp and avoid system
server dirtying memory for these methods.

Test: m
Bug: 162110941
Change-Id: Ifda5957aab757fe47c97b1aee0a6a8b7a059ac3d