Fix incorrect pg_stat_io output on 32-bit machines.

pg_stat_get_io() applied TimestampTzGetDatum twice to the
stat_reset_timestamp value.  On 64-bit builds that's harmless because
TimestampTzGetDatum is a no-op, but on 32-bit builds it results in
displaying garbage in the stats_reset column of the pg_stat_io view.

Bug dates to commit a9c70b4 which introduced pg_stat_io, so
back-patch to v16 where that came in.

Bertrand Drouvot

Discussion: https://postgr.es/m/Ztrd+XcPTz1zorkg@ip-10-97-1-34.eu-west-3.compute.internal

Author: tglsfdc

src/backend/utils/adt/pgstatfuncs.c

@@ -1408,7 +1408,7 @@ pg_stat_get_io(PG_FUNCTION_ARGS)
 				values[IO_COL_BACKEND_TYPE] = bktype_desc;
 				values[IO_COL_CONTEXT] = CStringGetTextDatum(context_name);
 				values[IO_COL_OBJECT] = CStringGetTextDatum(obj_name);
-				values[IO_COL_RESET_TIME] = TimestampTzGetDatum(reset_time);
+				values[IO_COL_RESET_TIME] = reset_time;
 
 				/*
 				 * Hard-code this to the value of BLCKSZ for now. Future