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/storage/ipc/dsm.c

@@ -44,7 +44,6 @@
 #include "storage/pg_shmem.h"
 #include "storage/shmem.h"
 #include "utils/freepage.h"
-#include "utils/guc.h"
 #include "utils/memutils.h"
 #include "utils/resowner.h"
 

src/backend/storage/ipc/ipci.c

@@ -16,7 +16,6 @@
 
 #include "access/clog.h"
 #include "access/commit_ts.h"
-#include "access/heapam.h"
 #include "access/multixact.h"
 #include "access/nbtree.h"
 #include "access/subtrans.h"
@@ -53,8 +52,6 @@
 #include "storage/spin.h"
 #include "utils/guc.h"
 #include "utils/injection_point.h"
-#include "utils/snapmgr.h"
-#include "utils/wait_event.h"
 
 /* GUCs */
 int			shared_memory_type = DEFAULT_SHARED_MEMORY_TYPE;

src/backend/storage/ipc/latch.c

@@ -60,7 +60,6 @@
 #include "storage/ipc.h"
 #include "storage/latch.h"
 #include "storage/pmsignal.h"
-#include "storage/shmem.h"
 #include "utils/memutils.h"
 #include "utils/resowner.h"
 

src/backend/storage/ipc/procarray.c

@@ -47,7 +47,6 @@
 
 #include <signal.h>
 
-#include "access/clog.h"
 #include "access/subtrans.h"
 #include "access/transam.h"
 #include "access/twophase.h"

src/backend/storage/ipc/procsignal.c

@@ -27,7 +27,6 @@
 #include "storage/condition_variable.h"
 #include "storage/ipc.h"
 #include "storage/latch.h"
-#include "storage/proc.h"
 #include "storage/shmem.h"
 #include "storage/smgr.h"
 #include "storage/sinval.h"

src/backend/storage/ipc/shm_mq.c

@@ -22,7 +22,6 @@
 #include "pgstat.h"
 #include "port/pg_bitutils.h"
 #include "postmaster/bgworker.h"
-#include "storage/procsignal.h"
 #include "storage/shm_mq.h"
 #include "storage/spin.h"
 #include "utils/memutils.h"

src/backend/storage/ipc/shmem.c

@@ -65,7 +65,6 @@
 
 #include "postgres.h"
 
-#include "access/transam.h"
 #include "fmgr.h"
 #include "funcapi.h"
 #include "miscadmin.h"

src/backend/storage/ipc/signalfuncs.c

@@ -24,7 +24,7 @@
 #include "storage/proc.h"
 #include "storage/procarray.h"
 #include "utils/acl.h"
-#include "utils/builtins.h"
+#include "utils/fmgrprotos.h"
 
 
 /*

src/backend/storage/ipc/sinval.c

@@ -15,10 +15,8 @@
 #include "postgres.h"
 
 #include "access/xact.h"
-#include "commands/async.h"
 #include "miscadmin.h"
-#include "storage/ipc.h"
-#include "storage/proc.h"
+#include "storage/latch.h"
 #include "storage/sinvaladt.h"
 #include "utils/inval.h"
 

src/backend/storage/ipc/standby.c

@@ -26,13 +26,11 @@
 #include "pgstat.h"
 #include "replication/slot.h"
 #include "storage/bufmgr.h"
-#include "storage/lmgr.h"
 #include "storage/proc.h"
 #include "storage/procarray.h"
 #include "storage/sinvaladt.h"
 #include "storage/standby.h"
 #include "utils/hsearch.h"
-#include "utils/memutils.h"
 #include "utils/ps_status.h"
 #include "utils/timeout.h"
 #include "utils/timestamp.h"