Add variable PRODUCT_SHIPPING_API_LEVEL.

PRODUCT_SHIPPING_API_LEVEL declares which API level a device first
shipped with.

We use this variable to set a read-only property that can be used in
CTS/GTS tests.

Bug: 26381401
Change-Id: I9dfeaf423146c35f57e69ac26c27e8a9e205bc4f
2 files changed