Revert "Skip WAL for new relfilenodes, under wal_level=minimal."

This reverts commit cb2fd7eac2.  Per
numerous buildfarm members, it was incompatible with parallel query, and
a test case assumed LP64.  Back-patch to 9.5 (all supported versions).

Discussion: https://postgr.es/m/20200321224920.GB1763544@rfd.leadboat.com

src/include/access/gist_private.h

@@ -448,8 +448,6 @@ extern XLogRecPtr gistXLogSplit(bool page_is_leaf,
 								BlockNumber origrlink, GistNSN oldnsn,
 								Buffer leftchild, bool markfollowright);
 
-extern XLogRecPtr gistXLogAssignLSN(void);
-
 /* gistget.c */
 extern bool gistgettuple(IndexScanDesc scan, ScanDirection dir);
 extern int64 gistgetbitmap(IndexScanDesc scan, TIDBitmap *tbm);

src/include/access/gistxlog.h

@@ -26,7 +26,6 @@
  /* #define XLOG_GIST_INSERT_COMPLETE	 0x40 */	/* not used anymore */
  /* #define XLOG_GIST_CREATE_INDEX		 0x50 */	/* not used anymore */
 #define XLOG_GIST_PAGE_DELETE		0x60
-#define XLOG_GIST_ASSIGN_LSN		0x70	/* nop, assign new LSN */
 
 /*
  * Backup Blk 0: updated page.

src/include/access/heapam.h

@@ -29,6 +29,7 @@
 
 
 /* "options" flag bits for heap_insert */
+#define HEAP_INSERT_SKIP_WAL	TABLE_INSERT_SKIP_WAL
 #define HEAP_INSERT_SKIP_FSM	TABLE_INSERT_SKIP_FSM
 #define HEAP_INSERT_FROZEN		TABLE_INSERT_FROZEN
 #define HEAP_INSERT_NO_LOGICAL	TABLE_INSERT_NO_LOGICAL

src/include/access/rewriteheap.h

@@ -23,7 +23,7 @@ typedef struct RewriteStateData *RewriteState;
 
 extern RewriteState begin_heap_rewrite(Relation OldHeap, Relation NewHeap,
 									   TransactionId OldestXmin, TransactionId FreezeXid,
-									   MultiXactId MultiXactCutoff);
+									   MultiXactId MultiXactCutoff, bool use_wal);
 extern void end_heap_rewrite(RewriteState state);
 extern void rewrite_heap_tuple(RewriteState state, HeapTuple oldTuple,
 							   HeapTuple newTuple);

src/include/access/tableam.h

@@ -128,7 +128,7 @@ typedef struct TM_FailureData
 } TM_FailureData;
 
 /* "options" flag bits for table_tuple_insert */
-/* TABLE_INSERT_SKIP_WAL was 0x0001; RelationNeedsWAL() now governs */
+#define TABLE_INSERT_SKIP_WAL		0x0001
 #define TABLE_INSERT_SKIP_FSM		0x0002
 #define TABLE_INSERT_FROZEN			0x0004
 #define TABLE_INSERT_NO_LOGICAL		0x0008
@@ -410,8 +410,9 @@ typedef struct TableAmRoutine
 
 	/*
 	 * Perform operations necessary to complete insertions made via
-	 * tuple_insert and multi_insert with a BulkInsertState specified. In-tree
-	 * access methods ceased to use this.
+	 * tuple_insert and multi_insert with a BulkInsertState specified. This
+	 * may for example be used to flush the relation, when the
+	 * TABLE_INSERT_SKIP_WAL option was used.
 	 *
 	 * Typically callers of tuple_insert and multi_insert will just pass all
 	 * the flags that apply to them, and each AM has to decide which of them
@@ -1100,6 +1101,10 @@ table_compute_xid_horizon_for_tuples(Relation rel,
  * The options bitmask allows the caller to specify options that may change the
  * behaviour of the AM. The AM will ignore options that it does not support.
  *
+ * If the TABLE_INSERT_SKIP_WAL option is specified, the new tuple doesn't
+ * need to be logged to WAL, even for a non-temp relation. It is the AMs
+ * choice whether this optimization is supported.
+ *
  * If the TABLE_INSERT_SKIP_FSM option is specified, AMs are free to not reuse
  * free space in the relation. This can save some cycles when we know the
  * relation is new and doesn't contain useful amounts of free space.
@@ -1319,7 +1324,9 @@ table_tuple_lock(Relation rel, ItemPointer tid, Snapshot snapshot,
 
 /*
  * Perform operations necessary to complete insertions made via
- * tuple_insert and multi_insert with a BulkInsertState specified.
+ * tuple_insert and multi_insert with a BulkInsertState specified. This
+ * e.g. may e.g. used to flush the relation when inserting with
+ * TABLE_INSERT_SKIP_WAL specified.
  */
 static inline void
 table_finish_bulk_insert(Relation rel, int options)