backupccl: crash on SHOW BACKUP for database with table referencing type in other database

[thoszhang]

We have a bug that makes cross-database type references possible (#55709 (comment)). This makes backups not work with RESTORE or SHOW BACKUP. SHOW BACKUP will crash the node:

root@:26257/defaultdb> create type t as enum('foo');
CREATE TYPE

Time: 93ms total (execution 93ms / network 0ms)

root@:26257/defaultdb> create table tbl (a t);
CREATE TABLE

Time: 198ms total (execution 78ms / network 120ms)

root@:26257/defaultdb> create database otherdb;
CREATE DATABASE

Time: 56ms total (execution 56ms / network 0ms)

root@:26257/defaultdb> alter table tbl rename to otherdb.tbl;
NOTICE: renaming tables with a qualification is deprecated
HINT: use ALTER TABLE tbl RENAME TO tbl instead
RENAME TABLE

Time: 185ms total (execution 57ms / network 128ms)

root@:26257/defaultdb> backup otherdb to 'nodelocal://backup';
ERROR: failed to resolve targets specified in the BACKUP stmt: table "otherdb" does not exist
root@:26257/defaultdb> backup database otherdb to 'nodelocal://backup';
ERROR: host component of nodelocal URI must be a node ID: nodelocal://backup
root@:26257/defaultdb> backup database otherdb to 'nodelocal://1/backup';
        job_id       |  status   | fraction_completed | rows | index_entries | bytes
---------------------+-----------+--------------------+------+---------------+--------
  600147520773095425 | succeeded |                  1 |    0 |             0 |     0
(1 row)

Time: 366ms total (execution 366ms / network 0ms)

root@:26257/defaultdb> restore otherdb from 'nodelocal://1/backup' with into_db=newdb;
ERROR: failed to resolve targets in the BACKUP location specified by the RESTORE stmt, use SHOW BACKUP to find correct targets: type "t" has unknown ParentID 50
root@:26257/defaultdb> show backup 'nodelocal://1/backup';
ERROR: driver: bad connection
warning: connection lost!
opening new connection: all session settings will be lost
warning: error retrieving the transaction status: dial tcp [::1]:26257: connect: connection refused
warning: connection lost!
opening new connection: all session settings will be lost
warning: error retrieving the database name: dial tcp [::1]:26257: connect: connection refused