Implement `Stored` class

[jenetics]

The purpose of the Stored class is to make stored and non-stored DTOs distinguishable via the type system. E.g.

void update(final Collection<Stored<Record>> records) {
    ...
}

void insert(final Collection<Record> records) {
    ...
}

The Stored class contains the primary key and the actual row values.

[jenetics]

// Record definition.
public record Stored<K, T>(K id, T value) {
}

// New default method in 'RowParser' interface.
default <K> RowParser<Stored<K, T>>
stored(final RowParser<? extends K> keyParser) {
    return RowParser.compose(Stored::new, keyParser, this);
}

[jenetics]

Merged into r2.1.0.