Put auto-generated _getAcquireLocalRoles at the end of mro, removing it
from Base.
Also, document why it is treated specially here.
Also, add _getAcquireLocalRoles methods on a few leaf classes whose
instances fake being portal types, without actually being proper document
instances. At least, the ones which are detected in unit tests. The
proper fix would likely rather be to make them proper document classes,
but this carries data migration concerns which go beyond the scope of
this regression fix (_getAcquireLocalRoles was not possible to override
anymore).