Simplify newNode() by removing special cases

- Remove MemoryContextAllocZeroAligned(). It was supposed to be a
  faster version of MemoryContextAllocZero(), but modern compilers turn
  the MemSetLoop() into a call to memset() anyway, making it more or
  less identical to MemoryContextAllocZero(). That was the only user of
  MemSetTest, MemSetLoop, so remove those too, as well as palloc0fast().

- Convert newNode() to a static inline function. When this was
  originally originally written, it was written as a macro because
  testing showed that gcc didn't inline the size check as we
  intended. Modern compiler versions do, and now that it just calls
  palloc0() there is no size-check to inline anyway.

One nice effect is that the palloc0() takes one less argument than
MemoryContextAllocZeroAligned(), which saves a few instructions in the
callers of newNode().

Reviewed-by: Peter Eisentraut, Tom Lane, John Naylor, Thomas Munro
Discussion: https://www.postgresql.org/message-id/b51f1fa7-7e6a-4ecc-936d-90a8a1659e7c@iki.fi

src/backend/nodes/Makefile

@@ -23,7 +23,6 @@ OBJS = \
 	makefuncs.o \
 	multibitmapset.o \
 	nodeFuncs.o \
-	nodes.o \
 	outfuncs.o \
 	params.o \
 	print.o \

src/backend/nodes/meson.build

@@ -7,7 +7,6 @@ backend_sources += files(
   'makefuncs.c',
   'multibitmapset.c',
   'nodeFuncs.c',
-  'nodes.c',
   'params.c',
   'print.c',
   'read.c',

src/backend/nodes/nodes.c

@@ -1,31 +0,0 @@
-/*-------------------------------------------------------------------------
- *
- * nodes.c
- *	  support code for nodes (now that we have removed the home-brew
- *	  inheritance system, our support code for nodes is much simpler)
- *
- * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
- * Portions Copyright (c) 1994, Regents of the University of California
- *
- *
- * IDENTIFICATION
- *	  src/backend/nodes/nodes.c
- *
- * HISTORY
- *	  Andrew Yu			Oct 20, 1994	file creation
- *
- *-------------------------------------------------------------------------
- */
-#include "postgres.h"
-
-#include "nodes/nodes.h"
-
-/*
- * Support for newNode() macro
- *
- * In a GCC build there is no need for the global variable newNodeMacroHolder.
- * However, we create it anyway, to support the case of a non-GCC-built
- * loadable module being loaded into a GCC-built backend.
- */
-
-Node	   *newNodeMacroHolder;