Fix old-fd issues using global barriers everywhere.

Commits 4eb21763 and b74e94dc introduced a way to force every backend to
close all relation files, to fix an ancient Windows-only bug.

This commit extends that behavior to all operating systems and adds
a couple of extra barrier points, to fix a totally different class of
bug: the reuse of relfilenodes in scenarios that have no other kind of
cache invalidation to prevent file descriptor mix-ups.

In all releases, data corruption could occur when you moved a database
to another tablespace and then back again.  Despite that, no back-patch
for now as the infrastructure required is too new and invasive.  In
master only, since commit aa010514, it could also happen when using
CREATE DATABASE with a user-supplied OID or via pg_upgrade.

Author: Andres Freund <andres@anarazel.de>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Reviewed-by: Thomas Munro <thomas.munro@gmail.com>
Discussion: https://postgr.es/m/20220209220004.kb3dgtn2x2k2gtdm%40alap3.anarazel.de

src/include/pg_config_manual.h

@@ -152,17 +152,6 @@
 #define EXEC_BACKEND
 #endif
 
-/*
- * If USE_BARRIER_SMGRRELEASE is defined, certain code paths that unlink
- * directories will ask other backends to close all smgr file descriptors.
- * This is enabled on Windows, because otherwise unlinked but still open files
- * can prevent rmdir(containing_directory) from succeeding.  On other
- * platforms, it can be defined to exercise those code paths.
- */
-#if defined(WIN32)
-#define USE_BARRIER_SMGRRELEASE
-#endif
-
 /*
  * Define this if your operating system supports link()
  */