Renumber 2PC resource managers so that compared to 9.0, predicate lock rmgr

is added to the end, and existing resource managers keep their old ids.
We're not going to guarantee on-disk compatibility for 2PC state files over
major releases, but it seems better to avoid changing the ids them anyway.
It will help anyone who might want to write external tools to inspect the
state files to work with files from different versions, if nothing else.
Per complaint from Tom Lane.

src/include/access/twophase_rmgr.h

@@ -23,10 +23,10 @@ typedef uint8 TwoPhaseRmgrId;
  */
 #define TWOPHASE_RM_END_ID			0
 #define TWOPHASE_RM_LOCK_ID			1
-#define TWOPHASE_RM_PREDICATELOCK_ID	2
-#define TWOPHASE_RM_PGSTAT_ID		3
-#define TWOPHASE_RM_MULTIXACT_ID	4
-#define TWOPHASE_RM_MAX_ID			TWOPHASE_RM_MULTIXACT_ID
+#define TWOPHASE_RM_PGSTAT_ID		2
+#define TWOPHASE_RM_MULTIXACT_ID	3
+#define TWOPHASE_RM_PREDICATELOCK_ID	4
+#define TWOPHASE_RM_MAX_ID			TWOPHASE_RM_PREDICATELOCK_ID
 
 extern const TwoPhaseCallback twophase_recover_callbacks[];
 extern const TwoPhaseCallback twophase_postcommit_callbacks[];