When generating a CE key, don't persist it immediately with
kEmptyAuthentication. Instead, cache it in memory and persist it later
when the secret to protect it with is given. This is needed to make it
so that the CE key is always encrypted by the user's synthetic password
while it is stored on-disk. See the corresponding system_server changes
for more information about this design change and its motivation.
As part of this, simplify vold's Binder interface by replacing the three
methods addUserKeyAuth(), clearUserKeyAuth(), and
fixateNewestUserKeyAuth() with a single method setUserKeyProtection().
setUserKeyProtection() handles persisting the key for a new user or
re-encrypting the default-encrypted key for an existing unsecured user.
Bug: 232452368
Ignore-AOSP-First: This depends on frameworks/base changes that can only
be submitted to internal master, due to conflicts.
Test: see Ia753ea21bbaca8ef7a90c03fe73b66c896b1536e
Change-Id: Id36ba8ee343ccb6de7ec892c3f600abd636f6ce5
8c1659e271