Avoid including tableam.h and xlogreader.h in nbtree.h

Doing that seems rather random and unnecessary.  This commit removes
those and fixes fallout, which is pretty minimal.  We do need to add a
forward declaration of struct TM_IndexDeleteOp (whose full definition
appears in tableam.h) so that _bt_delitems_delete_check()'s declaration
can use it.

Author: Álvaro Herrera <alvherre@kurilemu.de>
Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Discussion: https://postgr.es/m/202508051109.lzk3lcuzsaxo@alvherre.pgsql

src/backend/access/nbtree/nbtdedup.c

@@ -16,6 +16,7 @@
 
 #include "access/nbtree.h"
 #include "access/nbtxlog.h"
+#include "access/tableam.h"
 #include "access/xloginsert.h"
 #include "miscadmin.h"
 #include "utils/rel.h"

src/backend/access/nbtree/nbtinsert.c

@@ -17,6 +17,7 @@
 
 #include "access/nbtree.h"
 #include "access/nbtxlog.h"
+#include "access/tableam.h"
 #include "access/transam.h"
 #include "access/xloginsert.h"
 #include "common/int.h"

src/backend/access/nbtree/nbtpreprocesskeys.c

@@ -16,11 +16,13 @@
 #include "postgres.h"
 
 #include "access/nbtree.h"
+#include "access/relscan.h"
 #include "common/int.h"
 #include "lib/qunique.h"
 #include "utils/array.h"
 #include "utils/lsyscache.h"
 #include "utils/memutils.h"
+#include "utils/rel.h"
 
 typedef struct BTScanKeyPreproc
 {

src/backend/access/nbtree/nbtsort.c

@@ -44,6 +44,7 @@
 #include "access/parallel.h"
 #include "access/relscan.h"
 #include "access/table.h"
+#include "access/tableam.h"
 #include "access/xact.h"
 #include "catalog/index.h"
 #include "commands/progress.h"

src/backend/access/nbtree/nbtsplitloc.c

@@ -15,6 +15,7 @@
 #include "postgres.h"
 
 #include "access/nbtree.h"
+#include "access/tableam.h"
 #include "common/int.h"
 
 typedef enum

src/backend/access/nbtree/nbtutils.c

@@ -19,10 +19,13 @@
 
 #include "access/nbtree.h"
 #include "access/reloptions.h"
+#include "access/relscan.h"
 #include "commands/progress.h"
 #include "miscadmin.h"
 #include "utils/datum.h"
 #include "utils/lsyscache.h"
+#include "utils/rel.h"
+
 
 #define LOOK_AHEAD_REQUIRED_RECHECKS 	3
 #define LOOK_AHEAD_DEFAULT_DISTANCE 	5