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/hash/hash.c

@@ -23,13 +23,13 @@
 #include "access/relscan.h"
 #include "access/tableam.h"
 #include "access/xloginsert.h"
-#include "catalog/index.h"
 #include "commands/progress.h"
 #include "commands/vacuum.h"
 #include "miscadmin.h"
-#include "optimizer/plancat.h"
+#include "nodes/execnodes.h"
 #include "pgstat.h"
-#include "utils/builtins.h"
+#include "optimizer/plancat.h"
+#include "utils/fmgrprotos.h"
 #include "utils/index_selfuncs.h"
 #include "utils/rel.h"
 

src/backend/access/hash/hash_xlog.c

@@ -17,11 +17,8 @@
 #include "access/bufmask.h"
 #include "access/hash.h"
 #include "access/hash_xlog.h"
-#include "access/transam.h"
-#include "access/xlog.h"
 #include "access/xlogutils.h"
-#include "miscadmin.h"
-#include "storage/procarray.h"
+#include "storage/standby.h"
 
 /*
  * replay a hash index meta page

src/backend/access/hash/hashfunc.c

@@ -26,11 +26,9 @@
 
 #include "postgres.h"
 
-#include "access/hash.h"
-#include "catalog/pg_collation.h"
 #include "common/hashfn.h"
-#include "utils/builtins.h"
 #include "utils/float.h"
+#include "utils/fmgrprotos.h"
 #include "utils/pg_locale.h"
 #include "varatt.h"
 

src/backend/access/hash/hashinsert.c

@@ -19,8 +19,6 @@
 #include "access/hash_xlog.h"
 #include "access/xloginsert.h"
 #include "miscadmin.h"
-#include "storage/buf_internals.h"
-#include "storage/lwlock.h"
 #include "storage/predicate.h"
 #include "utils/rel.h"
 

src/backend/access/hash/hashpage.c

@@ -33,9 +33,9 @@
 #include "access/xloginsert.h"
 #include "miscadmin.h"
 #include "port/pg_bitutils.h"
-#include "storage/lmgr.h"
 #include "storage/predicate.h"
 #include "storage/smgr.h"
+#include "utils/rel.h"
 
 static bool _hash_alloc_buckets(Relation rel, BlockNumber firstblock,
 								uint32 nblocks);

src/backend/access/hash/hashutil.c

@@ -18,7 +18,6 @@
 #include "access/reloptions.h"
 #include "access/relscan.h"
 #include "port/pg_bitutils.h"
-#include "storage/buf_internals.h"
 #include "utils/lsyscache.h"
 #include "utils/rel.h"