[pm] make archiveTimeMillis as part of ArchiveState

Make this timestamp set at the time when ArchiveState is created. This
way we don't need to set the timestamp separately. The timestamp is
still preserved during serialization/deserialization. It will be deleted
along with the ArchiveState if the app is updated.

BUG: 310027113
Test: atest com.android.server.pm.PackageUserStateTest
Test: atest android.content.pm.cts.PackageInstallerArchiveTest#archiveApp_getArchiveTimeMillis
Test: atest android.content.pm.cts.PackageInstallerArchiveTest#archiveApp_archiveStateClearedAfterUpdate

Change-Id: I09f4f382ed3db21d4c45f9d9e93d15dcf9a07f2c