pgsql: psql: Add information in \d+ about foreign partitions and child

psql: Add information in \d+ about foreign partitions and child tables

\d+ is already able to show if a partition or a child table is
"PARTITIONED" via its relkind, hence the addition of a keyword for
"FOREIGN" in the relation description is basically free.

Author: Ian Lawrence Barwick
Reviewed-by: Tom Lane, Michael Paquier
Discussion: /messages/by-id/CAB8KJ=iwzbEz2HR9EhNxQLVhMk2G_OYtQPJ9V=jWLadseggrOA@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/bd95816f74ad4cad3d2a3c160be426358d6cea51

Modified Files
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src/bin/psql/describe.c | 2 ++
src/test/regress/expected/foreign_data.out | 36 +++++++++++++++---------------
2 files changed, 20 insertions(+), 18 deletions(-)