pgsql: Collect attribute data on extension owned tables being dumped

Collect attribute data on extension owned tables being dumped

If this data is not collected, pg_dump segfaults if asked for column
inserts.

Fix by Fabrízio de Royes Mello

Backpatch to release 12 where the bug was introduced.

Branch
------
REL_13_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/72857482c135677703111855f33550c442108eaa

Modified Files
--------------
src/bin/pg_dump/pg_dump.c                          |  4 ++++
src/test/modules/test_pg_dump/t/001_base.pl        | 24 ++++++++++++++++++++--
.../modules/test_pg_dump/test_pg_dump--1.0.sql     |  5 +++++
3 files changed, 31 insertions(+), 2 deletions(-)