pgsql: psql: Display stats target of extended statistics

psql: Display stats target of extended statistics

The stats target can be set since commit d06215d03, but wasn't shown by
psql.

Author: Justin Pryzby <justin@telsasoft.com>
Discussion: https://postgr.es/m/20200831050047.GG5450@telsasoft.com
Reviewed-by: Georgios Kokolatos <gkokolatos@protonmail.com>
Reviewed-by: Tatsuro Yamada <tatsuro.yamada.tf@nttcom.co.jp>

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3c99230b4f0d10c9eac5f4efdd2394eccb2af3a0

Modified Files
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src/bin/psql/describe.c                 | 14 ++++++++++++--
src/test/regress/expected/stats_ext.out | 18 ++++++++++++++++++
src/test/regress/sql/stats_ext.sql      |  2 ++
3 files changed, 32 insertions(+), 2 deletions(-)