Perform sql_pop delete in bulk instead of one-at-a-time.

Prior to 506104686b these DELETEs had been done in large batches (of
DEFAULT_PEEK_COUNT size), but that naive method of choosing rows to
delete was unsafe. Here we continue to keep track of which rows must
be deleted as we process them.

lib/pg_repack.sql.in

@@ -191,7 +191,7 @@ CREATE VIEW repack.tables AS
          'INSERT INTO repack.table_' || R.oid || ' VALUES ($1.*)' AS sql_insert,
          'DELETE FROM repack.table_' || R.oid || ' WHERE ' || repack.get_compare_pkey(PK.indexrelid, '$1') AS sql_delete,
          'UPDATE repack.table_' || R.oid || ' SET ' || repack.get_assign(R.oid, '$2') || ' WHERE ' || repack.get_compare_pkey(PK.indexrelid, '$1') AS sql_update,
-         'DELETE FROM repack.log_' || R.oid || ' WHERE id = $1' AS sql_pop
+         'DELETE FROM repack.log_' || R.oid || ' WHERE id IN (' AS sql_pop
     FROM pg_class R
          LEFT JOIN pg_class T ON R.reltoastrelid = T.oid
          LEFT JOIN repack.primary_keys PK