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: /messages/by-id/7075d3aa-3f05-44a5-b68f-47dc6a8a0550@buildkite.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/7418767f11d11ca4003ed3e8e96296eabb2acfe1

Modified Files
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src/bin/pg_dump/pg_dump.c | 30 +++++++++++++++++++++++++++---
src/bin/pg_dump/pg_dump.h | 3 ++-
src/bin/pg_dump/t/002_pg_dump.pl | 5 +++--
3 files changed, 32 insertions(+), 6 deletions(-)