pgsql: In pg_dump, don't dump a stats object unless dumping underlying

In pg_dump, don't dump a stats object unless dumping underlying table.

If the underlying table isn't being dumped, it's useless to dump
an extended statistics object; it'll just cause errors at restore.
We have always applied similar policies to, say, indexes.

(When and if we get cross-table stats objects, it might be profitable
to think a little harder about what to do with them.  But for now
there seems no point in considering a stats object as anything but
an appendage of its table.)

Rian McGuire and Tom Lane, per report from Rian McGuire.
Back-patch to supported branches.

Discussion: https://postgr.es/m/7075d3aa-3f05-44a5-b68f-47dc6a8a0550@buildkite.com

Branch
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REL_14_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/aa2e323eedc9e3cbad4eae19b309f92c8ba8afeb

Modified Files
--------------
src/bin/pg_dump/pg_dump.c        | 30 +++++++++++++++++++++++++++---
src/bin/pg_dump/pg_dump.h        |  1 +
src/bin/pg_dump/t/002_pg_dump.pl |  6 +++---
3 files changed, 31 insertions(+), 6 deletions(-)