Add PolicyDirection InfDef annotation to IpSecManager

IpSec is going to be moved into Connectivity module and it needs to
use PolicyDirection annotation. Add PolicyDirection IntDef annotation
so that it can be used in the module.

Bug: 204153604
Test: FrameworksNetTests
Change-Id: Ib411d8c436d67574bfaf7f3aba43e5f31e7487e2