pgsql: pg_dump: Fix inherited flag in extended stats from pre-v15 serve

pg_dump: Fix inherited flag in extended stats from pre-v15 servers

Servers older than v15 have no stxdinherit in pg_statistic_ext_data, so
pg_dump hardcoded it to false. However, these versions build inherited
extended stats on partitioned tables since 20b9fa308eb. Once restored
as non-inherited, the data was ignored by the planner. pg_upgrade from
v10~v14 was impacted by this issue.

For servers in this range, the inherited flag is now guessed from the
relkind of the relation: true for partitioned tables and false
otherwise, matching with what ANALYZE did before 269b532aef5
(introduction of pg_statistic_ext_data.stxdinherit).

Oversight in c32fb29e979d.

Author: Artem Gavrilov <artem(dot)gavrilov(at)percona(dot)com>
Reviewed-by: Corey Huinker <corey(dot)huinker(at)gmail(dot)com>
Reviewed-by: Michael Paquier <michael(at)paquier(dot)xyz>
Discussion: https://postgr.es/m/CAFPkQKxoB=kBdVsHXHvprV5j2OOBP5x5ea2yL9h0d3HtjuX+Sg@mail.gmail.com
Backpatch-through: 19

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/35def3385998099f3e80e34f9d7bf6444af5bf1c

Modified Files
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src/bin/pg_dump/pg_dump.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)