pgsql: Pass constructName to transformJsonValueExpr()

Pass constructName to transformJsonValueExpr()

This allows it to pass to coerce_to_specific_type() the actual name
corresponding to the specific JSON_* function expression being
transformed, instead of the currently hardcoded string.

Backpatched to 16 from the development branch to keep the code in
sync across branches.

Reviewed-by: Álvaro Herrera <alvherre@alvh.no-ip.org>
Discussion: https://postgr.es/m/CA+HiwqHu58pO3cJ7rB6ZLwUztVdG1J66xSjDdjfan5uT5NhESw@mail.gmail.com

Branch
------
REL_16_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/7825a1b01e400434835253b4ff38dd96d823d454

Modified Files
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src/backend/parser/parse_expr.c | 24 +++++++++++++-----------
1 file changed, 13 insertions(+), 11 deletions(-)