Una riga per contatto:
SELECT
contacts.id,
contacts.first_name,
contacts.last_name,
GROUP_CONCAT(IF(field_values.field_id = 2, field_values.value, NULL)) AS email,
GROUP_CONCAT(IF(field_values.field_id = 1, field_values.value, NULL)) AS field_1
FROM contacts
LEFT JOIN field_values ON contacts.id = field_values.contact_id
GROUP BY contacts.id
ORDER BY email;. -- it is optional, only include if you want to sort result by ascending emails.