pgsql: SQL/JSON: Improve some error messages

SQL/JSON: Improve some error messages

This improves some error messages emitted by SQL/JSON query functions
by mentioning column name when available, such as when they are
invoked as part of evaluating JSON_TABLE() columns.  To do so, a new
field column_name is added to both JsonFuncExpr and JsonExpr that is
only populated when creating those nodes for transformed JSON_TABLE()
columns.

While at it, relevant error messages are reworded for clarity.

Reported-by: Jian He <jian.universality@gmail.com>
Suggested-by: Jian He <jian.universality@gmail.com>
Discussion: https://postgr.es/m/CACJufxG_e0QLCgaELrr2ZNz7AxPeGCNKAORe3fHtFCQLsH4J4Q@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/b4fad46b6bc8a9bf46ff689bcb1bd4edf8f267af

Modified Files
--------------
src/backend/executor/execExprInterp.c            | 43 ++++++++++++----------
src/backend/parser/parse_expr.c                  |  1 +
src/backend/parser/parse_jsontable.c             | 10 +++---
src/backend/utils/adt/jsonpath_exec.c            | 45 +++++++++++++++++-------
src/include/nodes/parsenodes.h                   |  2 ++
src/include/nodes/primnodes.h                    |  3 ++
src/include/utils/jsonpath.h                     |  6 ++--
src/test/regress/expected/sqljson_jsontable.out  | 10 ++++--
src/test/regress/expected/sqljson_queryfuncs.out | 30 ++++++++--------
src/test/regress/sql/sqljson_jsontable.sql       |  3 ++
10 files changed, 96 insertions(+), 57 deletions(-)