Add ephemeral protection level

Ephemeral applications will only be able to be granted permissions that
have the ephemeral proteciton level, this allows us to tighly define
what behavior is OK for ephemeral applications.

This includes an initial small whitelist of permissions for ephemeral
apps, it may be expanded later.

Test: adb install --ephemeral, verified against both runtime and install
time permissions
Test: cts-tradefed run cts -m CtsPermission2TestCases
Change-Id: I854c44cf7a293d484b674cdd4fb5141e362a2f1a