Stop using FDE-related constants from IVold

IVold.ENCRYPTION_STATE_* and IVold.PASSWORD_TYPE_* are values returned
by or accepted by FDE-specific vold methods, which are no longer used.
Stop using these constants so that we can remove them from IVold.aidl.

Notes on specific constants:

- Some constants have @UnsupportedAppUsage.  There is no reason why a
  non-system app should have been using these.  However, to avoid
  possibly breaking apps I just left these with hardcoded values.

- StorageManager.CRYPT_TYPE_* are used by
  LockscreenCredential.getStorageCryptType().  However, the caller of
  this method was removed by an earlier CL, so just remove this method.

- StorageManager.CRYPT_TYPE_* also have a user in
  packages/apps/Settings, but it is obsolete code that I'm removing in
  another CL.

Bug: 208476087
Change-Id: I41c684b69a97dbafac65d8f55db2c284d7a8dd70