Ajustes no manager RegularPressReleaseCustomManager.by_journal_pid para realizar uma query mais eficiente ao BD

A query resultante deste ticket ficou assim:

```sql
SELECT "journalmanager_pressrelease"."id", 
       "journalmanager_pressrelease"."doi", 
       "journalmanager_regularpressrelease"."pressrelease_ptr_id", 
       "journalmanager_regularpressrelease"."issue_id" 
FROM "journalmanager_regularpressrelease" 
    INNER JOIN "journalmanager_pressrelease" 
    ON ("journalmanager_regularpressrelease"."pressrelease_ptr_id" = "journalmanager_pressrelease"."id") 
    WHERE "journalmanager_regularpressrelease"."pressrelease_ptr_id" IN (
        SELECT U0."pressrelease_ptr_id" 
        FROM "journalmanager_regularpressrelease" U0 
        INNER JOIN "journalmanager_issue" U1 
        ON (U0."issue_id" = U1."id") 
        WHERE U1."journal_id" IN (
            SELECT U0."id" 
            FROM "journalmanager_journal" U0 
            WHERE (U0."print_issn" = '0034-8910'  OR U0."eletronic_issn" = '0034-8910' ))) 
LIMIT 20;

```

O uso de subqueries e pré-carga das traduções fez com que o endpoint *pressreleases* melhorasse o desempenho em aproximadamente 50%, de acordo com medição tosca.