May be useful to interface with some external program, e.g. I want to use `clickhouse-format` to beautify the queries for performance test reports.

For now, DDL dictionaries don't work for `clickhouse-local` at all (https://github.com/ClickHouse/ClickHouse/issues/22354)

We should do it through DDL, because the xml config route looks hopeless. `clickhouse-local` can't even load server's `config.xml` properly.
{
    return true;
}
bool ExecutablePoolDictionarySource::supportsSelectiveLoad() const