API that reports first SDK level of the device.

This is different from SDK_INT, which can change due to OTA
software updates.

Test: cts-tradefed run commandAndExit cts-dev -m CtsOsTestCases -t android.os.cts.BuildTest
Bug: 69270887
Change-Id: Ic3f4b22b25dc08f3fbdbdf7622c953323447ea01
6 files changed