StorageManagerService: rename mLocalUnlockedUsers to mCeUnlockedUsers

mLocalUnlockedUsers contains the IDs of the users whose CE storage is
unlocked.  Rename it to mCeUnlockedUsers to make this clear.  Also
rename WatchedLockedUsers to WatchedUnlockedUsers.

No change in behavior except s/Local/CE/ in dump().

Bug: 306204742
Flag: exempt, mechanical refactoring
Test: presubmit
Change-Id: I11d13967564b04a9efc2cb20678677e71ef6e91b