Clean up date_part tests a bit

Some tests for timestamp and timestamptz were in the date.sql test
file.  Move them to their appropriate files, or drop tests cases that
were already present there.

src/test/regress/expected/date.out

@@ -971,18 +971,6 @@ SELECT EXTRACT(EPOCH FROM DATE        '1970-01-01');     --  0
          0
 (1 row)
 
-SELECT EXTRACT(EPOCH FROM TIMESTAMP   '1970-01-01');     --  0
- date_part 
------------
-         0
-(1 row)
-
-SELECT EXTRACT(EPOCH FROM TIMESTAMPTZ '1970-01-01+00');  --  0
- date_part 
------------
-         0
-(1 row)
-
 --
 -- century
 --
@@ -1137,22 +1125,6 @@ SELECT EXTRACT(DECADE FROM DATE '0012-12-31 BC'); --  -2
         -2
 (1 row)
 
---
--- some other types:
---
--- on a timestamp.
-SELECT EXTRACT(CENTURY FROM NOW())>=21 AS True;       -- true
- true 
-------
- t
-(1 row)
-
-SELECT EXTRACT(CENTURY FROM TIMESTAMP '1970-03-20 04:30:00.00000'); -- 20
- date_part 
------------
-        20
-(1 row)
-
 --
 -- all possible fields
 --
@@ -1370,7 +1342,7 @@ select isfinite('infinity'::date), isfinite('-infinity'::date), isfinite('today'
 (1 row)
 
 --
--- oscillating fields from non-finite date/timestamptz:
+-- oscillating fields from non-finite date:
 --
 SELECT EXTRACT(HOUR FROM DATE 'infinity');      -- NULL
  date_part 
@@ -1384,30 +1356,6 @@ SELECT EXTRACT(HOUR FROM DATE '-infinity');     -- NULL
           
 (1 row)
 
-SELECT EXTRACT(HOUR FROM TIMESTAMP   'infinity');      -- NULL
- date_part 
------------
-          
-(1 row)
-
-SELECT EXTRACT(HOUR FROM TIMESTAMP   '-infinity');     -- NULL
- date_part 
------------
-          
-(1 row)
-
-SELECT EXTRACT(HOUR FROM TIMESTAMPTZ 'infinity');      -- NULL
- date_part 
------------
-          
-(1 row)
-
-SELECT EXTRACT(HOUR FROM TIMESTAMPTZ '-infinity');     -- NULL
- date_part 
------------
-          
-(1 row)
-
 -- all possible fields
 SELECT EXTRACT(MICROSECONDS  FROM DATE 'infinity');    -- NULL
  date_part 
@@ -1500,7 +1448,7 @@ SELECT EXTRACT(TIMEZONE_H    FROM DATE 'infinity');    -- NULL
 (1 row)
 
 --
--- monotonic fields from non-finite date/timestamptz:
+-- monotonic fields from non-finite date:
 --
 SELECT EXTRACT(EPOCH FROM DATE 'infinity');         --  Infinity
  date_part 
@@ -1514,30 +1462,6 @@ SELECT EXTRACT(EPOCH FROM DATE '-infinity');        -- -Infinity
  -Infinity
 (1 row)
 
-SELECT EXTRACT(EPOCH FROM TIMESTAMP   'infinity');  --  Infinity
- date_part 
------------
-  Infinity
-(1 row)
-
-SELECT EXTRACT(EPOCH FROM TIMESTAMP   '-infinity'); -- -Infinity
- date_part 
------------
- -Infinity
-(1 row)
-
-SELECT EXTRACT(EPOCH FROM TIMESTAMPTZ 'infinity');  --  Infinity
- date_part 
------------
-  Infinity
-(1 row)
-
-SELECT EXTRACT(EPOCH FROM TIMESTAMPTZ '-infinity'); -- -Infinity
- date_part 
------------
- -Infinity
-(1 row)
-
 -- all possible fields
 SELECT EXTRACT(YEAR       FROM DATE 'infinity');    --  Infinity
  date_part 

src/test/regress/sql/date.sql

@@ -239,8 +239,6 @@ SELECT f1 as "date",
 -- epoch
 --
 SELECT EXTRACT(EPOCH FROM DATE        '1970-01-01');     --  0
-SELECT EXTRACT(EPOCH FROM TIMESTAMP   '1970-01-01');     --  0
-SELECT EXTRACT(EPOCH FROM TIMESTAMPTZ '1970-01-01+00');  --  0
 --
 -- century
 --
@@ -276,12 +274,6 @@ SELECT EXTRACT(DECADE FROM DATE '0002-12-31 BC'); --  -1
 SELECT EXTRACT(DECADE FROM DATE '0011-01-01 BC'); --  -1
 SELECT EXTRACT(DECADE FROM DATE '0012-12-31 BC'); --  -2
 --
--- some other types:
---
--- on a timestamp.
-SELECT EXTRACT(CENTURY FROM NOW())>=21 AS True;       -- true
-SELECT EXTRACT(CENTURY FROM TIMESTAMP '1970-03-20 04:30:00.00000'); -- 20
---
 -- all possible fields
 --
 SELECT EXTRACT(MICROSECONDS  FROM DATE '2020-08-11');
@@ -327,14 +319,10 @@ select 'infinity'::date > 'today'::date as t;
 select '-infinity'::date < 'today'::date as t;
 select isfinite('infinity'::date), isfinite('-infinity'::date), isfinite('today'::date);
 --
--- oscillating fields from non-finite date/timestamptz:
+-- oscillating fields from non-finite date:
 --
 SELECT EXTRACT(HOUR FROM DATE 'infinity');      -- NULL
 SELECT EXTRACT(HOUR FROM DATE '-infinity');     -- NULL
-SELECT EXTRACT(HOUR FROM TIMESTAMP   'infinity');      -- NULL
-SELECT EXTRACT(HOUR FROM TIMESTAMP   '-infinity');     -- NULL
-SELECT EXTRACT(HOUR FROM TIMESTAMPTZ 'infinity');      -- NULL
-SELECT EXTRACT(HOUR FROM TIMESTAMPTZ '-infinity');     -- NULL
 -- all possible fields
 SELECT EXTRACT(MICROSECONDS  FROM DATE 'infinity');    -- NULL
 SELECT EXTRACT(MILLISECONDS  FROM DATE 'infinity');    -- NULL
@@ -352,14 +340,10 @@ SELECT EXTRACT(TIMEZONE      FROM DATE 'infinity');    -- NULL
 SELECT EXTRACT(TIMEZONE_M    FROM DATE 'infinity');    -- NULL
 SELECT EXTRACT(TIMEZONE_H    FROM DATE 'infinity');    -- NULL
 --
--- monotonic fields from non-finite date/timestamptz:
+-- monotonic fields from non-finite date:
 --
 SELECT EXTRACT(EPOCH FROM DATE 'infinity');         --  Infinity
 SELECT EXTRACT(EPOCH FROM DATE '-infinity');        -- -Infinity
-SELECT EXTRACT(EPOCH FROM TIMESTAMP   'infinity');  --  Infinity
-SELECT EXTRACT(EPOCH FROM TIMESTAMP   '-infinity'); -- -Infinity
-SELECT EXTRACT(EPOCH FROM TIMESTAMPTZ 'infinity');  --  Infinity
-SELECT EXTRACT(EPOCH FROM TIMESTAMPTZ '-infinity'); -- -Infinity
 -- all possible fields
 SELECT EXTRACT(YEAR       FROM DATE 'infinity');    --  Infinity
 SELECT EXTRACT(DECADE     FROM DATE 'infinity');    --  Infinity

src/test/regress/sql/timestamp.sql

@@ -256,7 +256,8 @@ SELECT d1 as "timestamp",
    date_part( 'decade', d1) AS decade,
    date_part( 'century', d1) AS century,
    date_part( 'millennium', d1) AS millennium,
-   round(date_part( 'julian', d1)) AS julian
+   round(date_part( 'julian', d1)) AS julian,
+   date_part( 'epoch', d1) AS epoch
    FROM TIMESTAMP_TBL;
 
 -- TO_CHAR()

src/test/regress/sql/timestamptz.sql

@@ -262,7 +262,8 @@ SELECT d1 as timestamptz,
    date_part( 'decade', d1) AS decade,
    date_part( 'century', d1) AS century,
    date_part( 'millennium', d1) AS millennium,
-   round(date_part( 'julian', d1)) AS julian
+   round(date_part( 'julian', d1)) AS julian,
+   date_part( 'epoch', d1) AS epoch
    FROM TIMESTAMPTZ_TBL;
 
 SELECT d1 as timestamptz,