Use apex name when querying privapp allowlists

Per-apex allowlists are stored based on their path, which corresponds
to the apex name and *not* the apex package name. These are the same for
AOSP targets, but for Google specific ones, the apex package name
*typically* is of the form com.google.android.* instead of com.android.*.

Test: m
Bug: 190375768
Change-Id: Iba36509285bd75db294e369088a23b73458f3a8b