[pm] make ApplicationInfo.dataDir null if the data dir is deleted

To reflect the actual existence of the data dir. Also changes dumpsys to
print it for each user, because it's supposed to be different per user.

BUG: 288142708
Test: atest
android.content.pm.cts.PackageManagerShellCommandMultiUserTest#testUninstallWithKeepDataMultiUser

Change-Id: Ib761d55c907f7ac1836e282fcc0d4563fbf790fb