Remove COMMIT_TS_SETTS record.

Commit 438fc4a39c prevented the WAL replay from writing
COMMIT_TS_SETTS record. By this change there is no code that
generates COMMIT_TS_SETTS record in PostgreSQL core.
Also we can think that there are no extensions using the record
because we've not received so far any complaints about the issue
that commit 438fc4a39c fixed. Therefore this commit removes
COMMIT_TS_SETTS record and its related code. Even without
this record, the timestamp required for commit timestamp feature
can be acquired from the COMMIT record.

Bump WAL page magic.

Reported-by: lx zou <zoulx1982@163.com>
Author: Fujii Masao
Reviewed-by: Alvaro Herrera
Discussion: https://postgr.es/m/16931-620d0f2fdc6108f1@postgresql.org

src/include/access/commit_ts.h

@@ -25,7 +25,7 @@ extern bool check_track_commit_timestamp(bool *newval, void **extra,
 
 extern void TransactionTreeSetCommitTsData(TransactionId xid, int nsubxids,
 										   TransactionId *subxids, TimestampTz timestamp,
-										   RepOriginId nodeid, bool write_xlog);
+										   RepOriginId nodeid);
 extern bool TransactionIdGetCommitTsData(TransactionId xid,
 										 TimestampTz *ts, RepOriginId *nodeid);
 extern TransactionId GetLatestCommitTsData(TimestampTz *ts,
@@ -50,7 +50,6 @@ extern int	committssyncfiletag(const FileTag *ftag, char *path);
 /* XLOG stuff */
 #define COMMIT_TS_ZEROPAGE		0x00
 #define COMMIT_TS_TRUNCATE		0x10
-#define COMMIT_TS_SETTS			0x20
 
 typedef struct xl_commit_ts_set
 {

src/include/access/xlog_internal.h

@@ -31,7 +31,7 @@
 /*
  * Each page of XLOG file has a header like this:
  */
-#define XLOG_PAGE_MAGIC 0xD10C	/* can be used as WAL version indicator */
+#define XLOG_PAGE_MAGIC 0xD10D	/* can be used as WAL version indicator */
 
 typedef struct XLogPageHeaderData
 {