pg_restore: fix incompatibility with old directory-format dumps.

pg_restore: fix incompatibility with old directory-format dumps.

pg_restore failed to restore large objects (blobs) out of
directory-format dumps made by versions before PG v12.
That's because, due to a bug fixed in commit 548e50976, those
old versions put the wrong filename into the BLOBS TOC entry.
Said bug was harmless before v17, because we ignored the
incorrect filename field --- but commit a45c78e32 assumed it
would be correct.

Reported-by: Pavel Stehule <pavel.stehule@gmail.com>
Author: Pavel Stehule <pavel.stehule@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/CAFj8pRCrZ=_e1Rv1N+6vDaH+6gf=9A2mE2J4RvnvKA1bLiXvXA@mail.gmail.com
Backpatch-through: 17