PIVOT_UNSUPPORTED_DATABASE_TYPES: ReadonlySet<string> = ...

The database types known not to run the engine's static pivot() (PLAN ยง11.12): H2 can't translate it, 13 types assert "pivot is not supported", Aurora asserts it too (the engine writes Aurora's SQL as Postgres's: read from its source, since the open-source engine loads no Aurora extension to plan with), and Trino and Athena plan it with no PIVOT. Snowflake, Databricks, MemSQL (SingleStore) and DuckDB run it; a type in neither list is allowed, for the engine to judge. A Set: the type comes from the model.