Change install name of privapp allowlists

Use the APK's filename as the on-device filename for the allowlist.
Previously the filename of the source xml file was used, which leads to
a problem when the same source file is used for different apps (even
if only one of those modules ends up being installed).

Bug: 284500052
Test: app_test.go & presubmit boot tests
Change-Id: I0b43a35e3a310464d79d7f37e0900d639f4a479c