Validate restore of NetworkPolicy settings

We want to catch potential exceptions that occur when restoring
NetworkPolicy settings. Here, a DateTimeException can be thrown when
we try to read the recurrence rule from the backup data and cannot
parse a timezone.

We also add GTS tests to validate that these catches persist and that
we don't crash when given unexpected backup data to restore.

Bug: 73942796
Test: gts-tradefed run gts -m GtsBackupHostTestCases -t com.google.android.gts.backup.NetworkPolicyRestoreHostSideTest
Change-Id: I6f6ea09d2fff60b8d704c6160234e6f032321103
(cherry picked from commit 853097ca)