Change internal queryid type from uint64 to int64

uint64 was perhaps chosen in cff440d36 as the type was uint32 prior to
that widening work.

Having this as uint64 doesn't make much sense and just adds the overhead of
having to remember that we always output this in its signed form.  Let's
remove that overhead.

The signed form output is seemingly required since we have no way to
represent the full range of uint64 in an SQL type.  We use BIGINT in places
like pg_stat_statements, which maps directly to int64.

The release notes "Source Code" section may want to mention this
adjustment as some extensions may wish to adjust their code.

Author: David Rowley <dgrowleyml@gmail.com>
Suggested-by: Peter Eisentraut <peter@eisentraut.org>
Reviewed-by: Sami Imseih <samimseih@gmail.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/50cb0c8b-994b-48f9-a1c4-13039eb3536b@eisentraut.org

src/backend/access/brin/brin.c

@@ -68,7 +68,7 @@ typedef struct BrinShared
 	int			scantuplesortstates;
 
 	/* Query ID, for report in worker processes */
-	uint64		queryid;
+	int64		queryid;
 
 	/*
 	 * workersdonecv is used to monitor the progress of workers.  All parallel

src/backend/access/nbtree/nbtsort.c

@@ -105,7 +105,7 @@ typedef struct BTShared
 	int			scantuplesortstates;
 
 	/* Query ID, for report in worker processes */
-	uint64		queryid;
+	int64		queryid;
 
 	/*
 	 * workersdonecv is used to monitor the progress of workers.  All parallel