Support for sqlc.embed

[masar3141]

As per the doc;

-- name: ScoreAndTests :many
SELECT sqlc.embed(students), sqlc.embed(test_scores)
FROM students
JOIN test_scores ON test_scores.student_id = students.id
WHERE students.id = $1;

produce this interface:

export interface ScoreAndTestsRow {
    students: string | null;
    testScores: string | null;
}

where we would expect

export interface ScoreAndTestsRow {
    students: Student;
    testScores: TestScore;
}