Support more createPackageContextAsUser() users.

We created this API to make it easy to pass a given UserHandle into
all Managers obtained from a given Context, which works great for
"normal" users, but we should also support special users like ALL
and CURRENT.

Also add an AutoCloseable marker to make try-with-resources easier.

Bug: 112153259
Test: atest android.content.cts.ContextTest
Change-Id: I261dfcc5cfdfc76bda5d70181785e11c2715a558