Give all users SP-based credentials

Make it so that every user gets a synthetic password (SP).  Previously,
users only got an SP if an LSKF or escrow token was set at least once.

For normally created users, create the SP by making UserManagerService
call the new method LSS.createNewUser(), just after the prerequisite
steps of createUserKey and prepareUserData.  As this now results in the
allocation of LSS state (e.g. a Weaver slot) before the user is fully
created, LSS can no longer rely on ACTION_USER_REMOVED for cleaning up
its state, so instead make UserManagerService.destroyUserState() call
LSS.removeUser().  Note that ACTION_USER_REMOVED isn't sent for
pre-created users, so as a side effect this change also fixes a bug
where LSS state for pre-created users wasn't removed immediately.

For the system user, which doesn't go through the normal user creation
flow, make LSS create the SP upon PHASE_BOOT_COMPLETED.  At the same
time, also create SPs for any other users who don't have one yet; this
handles users that were created by older versions of Android.

This change makes things more consistent.  It is also a prerequisite to
making it so that a Weaver value is always needed to unlock the CE key
if the device supports Weaver; this is important since Weaver may be the
only available securely erasable storage.  A later CL will implement
this by making the CE key be always bound to the SP.  For now, the CE
key remains unlockable separately from the SP when there is no LSKF.

Test: see Ia753ea21bbaca8ef7a90c03fe73b66c896b1536e
Bug: 232452368
Change-Id: Ic82084fe9d9bb34ee9640dea027963043afca9c2