Audit logs with JSON change sets, sessions and one-time tokens cannot be masked
column by column and typically come from vendor packages, so they cannot be
annotated - yet their views exposed readable names, session tokens and password
reset tokens to anyone with access to the anonymized schema.

- AnonymizationPolicy takes a list of excluded entities (subclasses included,
  unknown classes ignored) and answers isExcluded()
- the generator creates no view for them (an existing one is dropped as stale),
  PersonalDataColumns and SchemaDescriber (optional policy argument) skip them