pgsql: SQL/JSON: Fix JSON_QUERY(... WITH CONDITIONAL WRAPPER)

SQL/JSON: Fix JSON_QUERY(... WITH CONDITIONAL WRAPPER)

Currently, when WITH CONDITIONAL WRAPPER is specified, array wrappers
are applied even to a single SQL/JSON item if it is a scalar JSON
value, but this behavior does not comply with the standard.

To fix, apply wrappers only when there are multiple SQL/JSON items
in the result.

Reported-by: Peter Eisentraut <peter(at)eisentraut(dot)org>
Author: Peter Eisentraut <peter(at)eisentraut(dot)org>
Author: Amit Langote <amitlangote09(at)gmail(dot)com>
Reviewed-by: Andrew Dunstan <andrew(at)dunslane(dot)net>
Discussion: https://postgr.es/m/8022e067-818b-45d3-8fab-6e0d94d03626%40eisentraut.org
Backpatch-through: 17

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/e6c45d85dc168fb05b5ee5596a4de5167c9fe01f

Modified Files
--------------
src/backend/utils/adt/jsonpath_exec.c | 24 +++++++++---
src/test/regress/expected/sqljson_queryfuncs.out | 49 +++++++++++-------------
src/test/regress/sql/sqljson_queryfuncs.sql | 13 +++----
3 files changed, 48 insertions(+), 38 deletions(-)