Otapreopt: Add init script for A/B artifact move

Move the /data/ota -> /data/dalvik-cache move from the zygote into
a minimal shell script. Add an init rc file to execute the script
once /data is mounted. Add Makefile rules to pull these files in
with the rest of the A/B OTA dexopt components.

The move is motivated by the new naming scheme that includes the
slot name. Passing the slot name to the zygote would complicate
the process, while the value is immediately available in the script
through a simple getprop call.

Bug: 25612095
Bug: 28069686
Change-Id: I63e718d488662e1b1de2ce857629cb90aa4f611d