pgsql: Revert SQL/JSON features

Revert SQL/JSON features

The reverts the following and makes some associated cleanups:

commit f79b803dc: Common SQL/JSON clauses
commit f4fb45d15: SQL/JSON constructors
commit 5f0adec25: Make STRING an unreserved_keyword.
commit 33a377608: IS JSON predicate
commit 1a36bc9db: SQL/JSON query functions
commit 606948b05: SQL JSON functions
commit 49082c2cc: RETURNING clause for JSON() and JSON_SCALAR()
commit 4e34747c8: JSON_TABLE
commit fadb48b00: PLAN clauses for JSON_TABLE
commit 2ef6f11b0: Reduce running time of jsonb_sqljson test
commit 14d3f24fa: Further improve jsonb_sqljson parallel test
commit a6baa4bad: Documentation for SQL/JSON features
commit b46bcf7a4: Improve readability of SQL/JSON documentation.
commit 112fdb352: Fix finalization for json_objectagg and friends
commit fcdb35c32: Fix transformJsonBehavior
commit 4cd8717af: Improve a couple of sql/json error messages
commit f7a605f63: Small cleanups in SQL/JSON code
commit 9c3d25e17: Fix JSON_OBJECTAGG uniquefying bug
commit a79153b7a: Claim SQL standard compliance for SQL/JSON features
commit a1e7616d6: Rework SQL/JSON documentation
commit 8d9f9634e: Fix errors in copyfuncs/equalfuncs support for JSON node types.
commit 3c633f32b: Only allow returning string types or bytea from json_serialize
commit 67b26703b: expression eval: Fix EEOP_JSON_CONSTRUCTOR and EEOP_JSONEXPR size.

The release notes are also adjusted.

Backpatch to release 15.

Discussion: https://postgr.es/m/40d2c882-bcac-19a9-754d-4299e1d87ac7@postgresql.org

Branch
------
REL_15_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/96ef3237bf741c12390003e90a4d7115c0c854b7

Modified Files
--------------
doc/src/sgml/func.sgml | 1065 +-----------
doc/src/sgml/keywords/sql2016-02-reserved.txt | 1 -
doc/src/sgml/release-15.sgml | 93 --
src/backend/catalog/sql_features.txt | 30 +-
src/backend/commands/explain.c | 8 +-
src/backend/executor/execExpr.c | 359 +----
src/backend/executor/execExprInterp.c | 743 ---------
src/backend/executor/nodeTableFuncscan.c | 23 +-
src/backend/jit/llvm/llvmjit_expr.c | 18 -
src/backend/jit/llvm/llvmjit_types.c | 3 -
src/backend/nodes/copyfuncs.c | 566 -------
src/backend/nodes/equalfuncs.c | 442 -----
src/backend/nodes/makefuncs.c | 122 --
src/backend/nodes/nodeFuncs.c | 486 ------
src/backend/nodes/outfuncs.c | 175 --
src/backend/nodes/readfuncs.c | 213 ---
src/backend/optimizer/path/costsize.c | 3 +-
src/backend/optimizer/util/clauses.c | 78 -
src/backend/parser/Makefile | 1 -
src/backend/parser/gram.y | 1115 +------------
src/backend/parser/parse_clause.c | 12 +-
src/backend/parser/parse_collate.c | 7 -
src/backend/parser/parse_expr.c | 1502 -----------------
src/backend/parser/parse_jsontable.c | 732 ---------
src/backend/parser/parse_relation.c | 7 +-
src/backend/parser/parse_target.c | 40 -
src/backend/parser/parser.c | 16 -
src/backend/utils/adt/format_type.c | 4 -
src/backend/utils/adt/formatting.c | 45 +-
src/backend/utils/adt/json.c | 553 +------
src/backend/utils/adt/jsonb.c | 352 +---
src/backend/utils/adt/jsonb_util.c | 39 +-
src/backend/utils/adt/jsonfuncs.c | 71 +-
src/backend/utils/adt/jsonpath.c | 257 ---
src/backend/utils/adt/jsonpath_exec.c | 844 +---------
src/backend/utils/adt/ruleutils.c | 719 +--------
src/backend/utils/misc/queryjumble.c | 72 -
src/include/catalog/catversion.h | 2 +-
src/include/catalog/pg_aggregate.dat | 22 -
src/include/catalog/pg_proc.dat | 74 -
src/include/executor/execExpr.h | 98 --
src/include/executor/executor.h | 2 -
src/include/nodes/makefuncs.h | 12 -
src/include/nodes/nodes.h | 28 -
src/include/nodes/parsenodes.h | 287 ----
src/include/nodes/primnodes.h | 265 +--
src/include/parser/kwlist.h | 26 -
src/include/parser/parse_clause.h | 3 -
src/include/utils/formatting.h | 4 -
src/include/utils/json.h | 26 -
src/include/utils/jsonb.h | 33 -
src/include/utils/jsonfuncs.h | 7 -
src/include/utils/jsonpath.h | 37 -
src/interfaces/ecpg/preproc/ecpg.trailer | 41 +-
src/interfaces/ecpg/preproc/parse.pl | 2 -
src/interfaces/ecpg/preproc/parser.c | 14 -
src/test/regress/expected/json_sqljson.out | 24 -
src/test/regress/expected/jsonb_sqljson.out | 2135 -------------------------
src/test/regress/expected/opr_sanity.out | 6 +-
src/test/regress/expected/sqljson.out | 1320 ---------------
src/test/regress/parallel_schedule | 2 +-
src/test/regress/sql/json_sqljson.sql | 15 -
src/test/regress/sql/jsonb_sqljson.sql | 977 -----------
src/test/regress/sql/opr_sanity.sql | 6 +-
src/test/regress/sql/sqljson.sql | 471 ------
src/tools/pgindent/typedefs.list | 15 -
66 files changed, 350 insertions(+), 16420 deletions(-)