pgsql: Fix JSON_TABLE PLAN deparse to keep parentheses around nested jo

Fix JSON_TABLE PLAN deparse to keep parentheses around nested joins

get_json_table_plan() parenthesized the child of a parent/child
(OUTER/INNER) plan only when that child was a sibling (UNION/CROSS)
join, not when it was itself a parent/child join. A plan such as
PLAN (p0 OUTER (p1 INNER p11)) was therefore deparsed as
PLAN (p0 OUTER p1 INNER p11), which does not parse back to the same
plan tree -- a dump/restore hazard. Parenthesize the child whenever it
is not a bare path name, matching the logic already used for the
operands of sibling joins.

Reported-by: Thom Brown <thom(at)linux(dot)com>
Discussion: https://postgr.es/m/CAA-aLv7aZGSExnbjJRw8eKkoXbu34TdoKLLA2gPye3aHjO5OSA@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/160ef2751b524cbc797e59642543790c4a8132ec

Modified Files
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src/backend/utils/adt/ruleutils.c | 3 ++-
src/test/regress/expected/sqljson_jsontable.out | 29 +++++++++++++++++++++++++
src/test/regress/sql/sqljson_jsontable.sql | 15 +++++++++++++
3 files changed, 46 insertions(+), 1 deletion(-)