Mapper_Forgiving

Prior to the Typed migration, this was a distinct actor subclass overriding isStrict to retain exceptions instead of failing outright. Now that MapperResponse always carries both the successful results and any exceptions, strict-vs-forgiving is purely a decision made by the caller (see Master.doMap / Master.isForgiving), so this is an alias for Mapper -- kept as a separate name for source compatibility with existing call sites.