Remove unused #include's from backend .c files

as determined by include-what-you-use (IWYU)

While IWYU also suggests to *add* a bunch of #include's (which is its
main purpose), this patch does not do that.  In some cases, a more
specific #include replaces another less specific one.

Some manual adjustments of the automatic result:

- IWYU currently doesn't know about includes that provide global
  variable declarations (like -Wmissing-variable-declarations), so
  those includes are being kept manually.

- All includes for port(ability) headers are being kept for now, to
  play it safe.

- No changes of catalog/pg_foo.h to catalog/pg_foo_d.h, to keep the
  patch from exploding in size.

Note that this patch touches just *.c files, so nothing declared in
header files changes in hidden ways.

As a small example, in src/backend/access/transam/rmgr.c, some IWYU
pragma annotations are added to handle a special case there.

Discussion: https://www.postgresql.org/message-id/flat/af837490-6b2f-46df-ba05-37ea6a6653fc%40eisentraut.org

src/backend/access/gist/gist.c

@@ -21,9 +21,8 @@
 #include "commands/vacuum.h"
 #include "miscadmin.h"
 #include "nodes/execnodes.h"
-#include "storage/lmgr.h"
 #include "storage/predicate.h"
-#include "utils/builtins.h"
+#include "utils/fmgrprotos.h"
 #include "utils/index_selfuncs.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"

src/backend/access/gist/gistbuild.c

@@ -36,11 +36,10 @@
 
 #include "access/genam.h"
 #include "access/gist_private.h"
-#include "access/gistxlog.h"
 #include "access/tableam.h"
 #include "access/xloginsert.h"
-#include "catalog/index.h"
 #include "miscadmin.h"
+#include "nodes/execnodes.h"
 #include "optimizer/optimizer.h"
 #include "storage/bufmgr.h"
 #include "storage/bulk_write.h"

src/backend/access/gist/gistbuildbuffers.c

@@ -14,13 +14,9 @@
  */
 #include "postgres.h"
 
-#include "access/genam.h"
 #include "access/gist_private.h"
-#include "catalog/index.h"
-#include "miscadmin.h"
 #include "storage/buffile.h"
 #include "storage/bufmgr.h"
-#include "utils/memutils.h"
 #include "utils/rel.h"
 
 static GISTNodeBufferPage *gistAllocateNewPageBuffer(GISTBuildBuffers *gfbb);

src/backend/access/gist/gistget.c

@@ -20,7 +20,6 @@
 #include "lib/pairingheap.h"
 #include "miscadmin.h"
 #include "pgstat.h"
-#include "storage/lmgr.h"
 #include "storage/predicate.h"
 #include "utils/float.h"
 #include "utils/memutils.h"

src/backend/access/gist/gistproc.c

@@ -21,8 +21,8 @@
 
 #include "access/gist.h"
 #include "access/stratnum.h"
-#include "utils/builtins.h"
 #include "utils/float.h"
+#include "utils/fmgrprotos.h"
 #include "utils/geo_decls.h"
 #include "utils/sortsupport.h"
 

src/backend/access/gist/gistutil.c

@@ -18,13 +18,12 @@
 #include "access/gist_private.h"
 #include "access/htup_details.h"
 #include "access/reloptions.h"
-#include "catalog/pg_opclass.h"
 #include "common/pg_prng.h"
 #include "storage/indexfsm.h"
-#include "storage/lmgr.h"
 #include "utils/float.h"
 #include "utils/fmgrprotos.h"
 #include "utils/lsyscache.h"
+#include "utils/rel.h"
 #include "utils/snapmgr.h"
 #include "utils/syscache.h"
 

src/backend/access/gist/gistvalidate.c

@@ -21,7 +21,6 @@
 #include "catalog/pg_opclass.h"
 #include "catalog/pg_opfamily.h"
 #include "catalog/pg_type.h"
-#include "utils/builtins.h"
 #include "utils/lsyscache.h"
 #include "utils/regproc.h"
 #include "utils/syscache.h"

src/backend/access/gist/gistxlog.c

@@ -16,12 +16,10 @@
 #include "access/bufmask.h"
 #include "access/gist_private.h"
 #include "access/gistxlog.h"
-#include "access/heapam_xlog.h"
 #include "access/transam.h"
 #include "access/xloginsert.h"
 #include "access/xlogutils.h"
-#include "miscadmin.h"
-#include "storage/procarray.h"
+#include "storage/standby.h"
 #include "utils/memutils.h"
 #include "utils/rel.h"