Add a couple more tests for interval input decoding.

Cover some cases that would have been broken by a proposed patch,
but we failed to notice for lack of test coverage.  I'm pushing
this separately mainly to memorialize that it *is* our historical
behavior.

Discussion: https://postgr.es/m/1344498.1648920056@sss.pgh.pa.us

Author: tglsfdc

src/test/regress/expected/interval.out

@@ -826,6 +826,16 @@ SELECT  interval '+1 -1:00:00',
  1 day -01:00:00 | -1 days +01:00:00 | 1 year 2 mons -3 days +04:05:06.789 | -1 years -2 mons +3 days -04:05:06.789
 (1 row)
 
+-- cases that trigger sign-matching rules in the sql style
+SELECT  interval '-23 hours 45 min 12.34 sec',
+        interval '-1 day 23 hours 45 min 12.34 sec',
+        interval '-1 year 2 months 1 day 23 hours 45 min 12.34 sec',
+        interval '-1 year 2 months 1 day 23 hours 45 min +12.34 sec';
+   interval   |       interval       |          interval           |          interval           
+--------------+----------------------+-----------------------------+-----------------------------
+ -22:14:47.66 | -1 days +23:45:12.34 | -10 mons +1 day 23:45:12.34 | -10 mons +1 day 23:45:12.34
+(1 row)
+
 -- test output of couple non-standard interval values in the sql style
 SET IntervalStyle TO sql_standard;
 SELECT  interval '1 day -1 hours',
@@ -837,6 +847,16 @@ SELECT  interval '1 day -1 hours',
  +0-0 +1 -1:00:00 | +0-0 -1 +1:00:00 | +1-2 -3 +4:05:06.789 | -1-2 +3 -4:05:06.789
 (1 row)
 
+-- cases that trigger sign-matching rules in the sql style
+SELECT  interval '-23 hours 45 min 12.34 sec',
+        interval '-1 day 23 hours 45 min 12.34 sec',
+        interval '-1 year 2 months 1 day 23 hours 45 min 12.34 sec',
+        interval '-1 year 2 months 1 day 23 hours 45 min +12.34 sec';
+   interval   |    interval    |       interval       |       interval        
+--------------+----------------+----------------------+-----------------------
+ -23:45:12.34 | -1 23:45:12.34 | -1-2 -1 -23:45:12.34 | -0-10 +1 +23:45:12.34
+(1 row)
+
 -- test outputting iso8601 intervals
 SET IntervalStyle to iso_8601;
 select  interval '0'                                AS "zero",

src/test/regress/sql/interval.sql

@@ -258,13 +258,25 @@ SELECT  interval '+1 -1:00:00',
         interval '+1-2 -3 +4:05:06.789',
         interval '-1-2 +3 -4:05:06.789';
 
+-- cases that trigger sign-matching rules in the sql style
+SELECT  interval '-23 hours 45 min 12.34 sec',
+        interval '-1 day 23 hours 45 min 12.34 sec',
+        interval '-1 year 2 months 1 day 23 hours 45 min 12.34 sec',
+        interval '-1 year 2 months 1 day 23 hours 45 min +12.34 sec';
+
 -- test output of couple non-standard interval values in the sql style
 SET IntervalStyle TO sql_standard;
 SELECT  interval '1 day -1 hours',
         interval '-1 days +1 hours',
         interval '1 years 2 months -3 days 4 hours 5 minutes 6.789 seconds',
         - interval '1 years 2 months -3 days 4 hours 5 minutes 6.789 seconds';
 
+-- cases that trigger sign-matching rules in the sql style
+SELECT  interval '-23 hours 45 min 12.34 sec',
+        interval '-1 day 23 hours 45 min 12.34 sec',
+        interval '-1 year 2 months 1 day 23 hours 45 min 12.34 sec',
+        interval '-1 year 2 months 1 day 23 hours 45 min +12.34 sec';
+
 -- test outputting iso8601 intervals
 SET IntervalStyle to iso_8601;
 select  interval '0'                                AS "zero",