Install appSet using InstallFileWithExtraFilesZip

This fixes a bug that only the primary output of an appSet is installed
when the appSet is part of a flattened APEX.

Bug: 247072627
Test: m GoogleExtServices on a device using flattened APEX.
system/apex/com.android.extservices.gms/priv-app/GoogleExtServices@TM
has these apks:

GoogleExtServices.apk  GoogleExtServices-arm64_v8a.apk
GoogleExtServices-hdpi.apk  GoogleExtServices-ldpi.apk
GoogleExtServices-mdpi.apk  GoogleExtServices-tvdpi.apk
GoogleExtServices-xhdpi.apk  GoogleExtServices-xxhdpi.apk
GoogleExtServices-xxxhdpi.apk

(before the fix, there only was GoogleExtServices.apk)

Change-Id: Icbc4dd002f856a3f751badec781ad132c423ac9b