Move zygote init config to its own file.

This allows us to choose different configs depending on
whether or not the target is 64 capable, and what its preferred
default is.

bug: 13647418
Change-Id: Ie1ce4245a3add7544c87d27c635ee390f4062523
Merge "Move zygote init config to its own file."
auto-merger: merge in from aosp/master