Revert indexed and enlargable binary heap implementation.

This reverts commit b840508644 and bcb14f4abc. These commits were made
for commit 5bec1d6bc5 (Improve eviction algorithm in ReorderBuffer
using max-heap for many subtransactions). However, per discussion,
commit efb8acc0d0 replaced binary heap + index with pairing heap, and
made these commits unnecessary.

Reported-by: Jeff Davis
Discussion: https://postgr.es/m/12747c15811d94efcc5cda72d6b35c80d7bf3443.camel%40j-davis.com

src/backend/executor/nodeGatherMerge.c

@@ -422,7 +422,6 @@ gather_merge_setup(GatherMergeState *gm_state)
 	/* Allocate the resources for the merge */
 	gm_state->gm_heap = binaryheap_allocate(nreaders + 1,
 											heap_compare_slots,
-											false,
 											gm_state);
 }
 

src/backend/executor/nodeMergeAppend.c

@@ -125,7 +125,7 @@ ExecInitMergeAppend(MergeAppend *node, EState *estate, int eflags)
 	mergestate->ms_nplans = nplans;
 
 	mergestate->ms_slots = (TupleTableSlot **) palloc0(sizeof(TupleTableSlot *) * nplans);
-	mergestate->ms_heap = binaryheap_allocate(nplans, heap_compare_slots, false,
+	mergestate->ms_heap = binaryheap_allocate(nplans, heap_compare_slots,
 											  mergestate);
 
 	/*

src/backend/postmaster/pgarch.c

@@ -258,8 +258,7 @@ PgArchiverMain(char *startup_data, size_t startup_data_len)
 
 	/* Initialize our max-heap for prioritizing files to archive. */
 	arch_files->arch_heap = binaryheap_allocate(NUM_FILES_PER_DIRECTORY_SCAN,
-												ready_file_comparator, false,
-												NULL);
+												ready_file_comparator, NULL);
 
 	/* Initialize our memory context. */
 	archive_context = AllocSetContextCreate(TopMemoryContext,

src/backend/replication/logical/reorderbuffer.c

@@ -1303,7 +1303,6 @@ ReorderBufferIterTXNInit(ReorderBuffer *rb, ReorderBufferTXN *txn,
 	/* allocate heap */
 	state->heap = binaryheap_allocate(state->nr_txns,
 									  ReorderBufferIterCompare,
-									  false,
 									  state);
 
 	/* Now that the state fields are initialized, it is safe to return it. */

src/backend/storage/buffer/bufmgr.c

@@ -3014,7 +3014,6 @@ BufferSync(int flags)
 	 */
 	ts_heap = binaryheap_allocate(num_spaces,
 								  ts_ckpt_progress_comparator,
-								  false,
 								  NULL);
 
 	for (i = 0; i < num_spaces; i++)