pgsql: Code review for recent SQL/JSON commits

Code review for recent SQL/JSON commits

- At the last minute and for no particularly good reason, I changed the
  WITHOUT token to be marked especially for lookahead, from the one in
  WITHOUT TIME to the one in WITHOUT UNIQUE.  Study of upcoming patches
  (where a new WITHOUT ARRAY WRAPPER clause is added) showed me that the
  former was better, so put it back the way the original patch had it.

- update exprTypmod() for JsonConstructorExpr to return the typmod of
  the RETURNING clause, as a comment there suggested.  Perhaps it's
  possible for this to make a difference with datetime types, but I
  didn't try to build a test case.

- The nodeFuncs.c support code for new nodes was calling walker()
  directly instead of the WALK() macro as introduced by commit 1c27d16e6e5c.
  Modernize that.  Also add exprLocation() support for a couple of nodes
  that missed it.  Lastly, reorder the code more sensibly.

The WITHOUT_LA -> WITHOUT change means that stored rules containing
either WITHOUT TIME ZONE or WITHOUT UNIQUE KEYS would change
representation.  Therefore, bump catversion.

Discussion: https://postgr.es/m/20230329181708.e64g2tpy7jyufqkr@alvherre.pgsql

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/71bfd1543f8b68e1013d3e8540b6b5aaf98e02e9

Modified Files
--------------
src/backend/nodes/nodeFuncs.c        | 420 +++++++++++++++++++++--------------
src/backend/parser/gram.y            |   8 +-
src/backend/parser/parser.c          |   4 +-
src/include/catalog/catversion.h     |   2 +-
src/interfaces/ecpg/preproc/parser.c |   4 +-
5 files changed, 266 insertions(+), 172 deletions(-)