Remove SHM_QUEUE

Prior patches got rid of all the uses of SHM_QUEUE. ilist.h style lists are
more widely used and have an easier to use interface. As there are no users
left, remove SHM_QUEUE.

Reviewed-by: Thomas Munro <thomas.munro@gmail.com> (in an older version)
Discussion: https://postgr.es/m/20221120055930.t6kl3tyivzhlrzu2@awork3.anarazel.de
Discussion: https://postgr.es/m/20200211042229.msv23badgqljrdg2@alap3.anarazel.de

Author: anarazel

src/backend/storage/ipc/Makefile

@@ -21,7 +21,6 @@ OBJS = \
 	shm_mq.o \
 	shm_toc.o \
 	shmem.o \
-	shmqueue.o \
 	signalfuncs.o \
 	sinval.o \
 	sinvaladt.o \

src/backend/storage/ipc/meson.build

@@ -13,7 +13,6 @@ backend_sources += files(
   'shm_mq.c',
   'shm_toc.c',
   'shmem.c',
-  'shmqueue.c',
   'signalfuncs.c',
   'sinval.c',
   'sinvaladt.c',

src/backend/storage/ipc/shmqueue.c

@@ -24,13 +24,6 @@
 #include "utils/hsearch.h"
 
 
-/* shmqueue.c */
-typedef struct SHM_QUEUE
-{
-	struct SHM_QUEUE *prev;
-	struct SHM_QUEUE *next;
-} SHM_QUEUE;
-
 /* shmem.c */
 extern void InitShmemAccess(void *seghdr);
 extern void InitShmemAllocation(void);
@@ -63,19 +56,4 @@ typedef struct
 	Size		allocated_size; /* # bytes actually allocated */
 } ShmemIndexEnt;
 
-/*
- * prototypes for functions in shmqueue.c
- */
-extern void SHMQueueInit(SHM_QUEUE *queue);
-extern void SHMQueueElemInit(SHM_QUEUE *queue);
-extern void SHMQueueDelete(SHM_QUEUE *queue);
-extern void SHMQueueInsertBefore(SHM_QUEUE *queue, SHM_QUEUE *elem);
-extern void SHMQueueInsertAfter(SHM_QUEUE *queue, SHM_QUEUE *elem);
-extern Pointer SHMQueueNext(const SHM_QUEUE *queue, const SHM_QUEUE *curElem,
-							Size linkOffset);
-extern Pointer SHMQueuePrev(const SHM_QUEUE *queue, const SHM_QUEUE *curElem,
-							Size linkOffset);
-extern bool SHMQueueEmpty(const SHM_QUEUE *queue);
-extern bool SHMQueueIsDetached(const SHM_QUEUE *queue);
-
 #endif							/* SHMEM_H */

src/include/storage/shmem.h

@@ -2377,7 +2377,6 @@ SERIALIZABLEXIDTAG
 SERVICE_STATUS
 SERVICE_STATUS_HANDLE
 SERVICE_TABLE_ENTRY
-SHM_QUEUE
 SID_AND_ATTRIBUTES
 SID_IDENTIFIER_AUTHORITY
 SID_NAME_USE