Remove unused code around getLastPackageUsageTimeInMills.

1. Remove the code for version 0. Version 1 was introduced in 2016
   (commit ca82e616), so there's no
   point to keep the support for version 0.
2. Remove leftover code from PackageParser. There are a value and a
   getter, but the value is never set. The functionality was moved to
   AndroidPackageWrite by
   commit 14ff7171, but the old code
   were left in PackageParser and nobody sets the value there since
   then.
3. Remove unused methods from PackageStateUnserialized and
   PackageSetting.

Bug: 258223472
Bug: 6527146
Test: Presubmit
Flag: EXEMPT cleanup
Change-Id: Ic53352fa575a76f76310f6384a94e44681ad235f