BUG #18585: Date/time conversion functions are not protected against integer overflow

The following bug has been logged on the website:

Bug reference: 18585
Logged by: Alexander Lakhin
Email address: exclusion(at)gmail(dot)com
PostgreSQL version: 17beta3
Operating system: Ubuntu 22.04
Description:

The date/time conversion functions do_to_timestamp(), DCH_from_char(),
... lack reliable checks for integer overflow in the input components.

1) Millennium:
SELECT to_timestamp('2147483647,999', 'Y,YYY');
to_timestamp
---------------------------
0001-01-01 00:00:00+00 BC
vs
SELECT to_timestamp('2147483,999', 'Y,YYY');
ERROR: timestamp out of range

2) Century:
SELECT to_date('-2147483648', 'CC');
to_date
------------
0001-01-01
vs
SELECT to_date('-21474836', 'CC');
ERROR: date out of range: "-21474836"

3) Century + year:
SELECT to_date('-2147483648 01', 'CC YY');
to_date
------------
0100-01-01
vs
SELECT to_date('-21474836 01', 'CC YY');
ERROR: date out of range: "-21474836 01"

4) Milliseconds:
SELECT to_timestamp('0.-2147483648', 'SS.MS');
to_timestamp
---------------------------
0001-01-01 00:00:00+00 BC
vs
SELECT to_timestamp('0.-2147483', 'SS.MS');
ERROR: date/time field value out of range: "0.-2147483"

5) Week of month:
SELECT to_timestamp('613566758', 'W');
to_timestamp
---------------------------
0001-01-04 00:00:00+00 BC
vs
SELECT to_timestamp('613566750', 'W');
ERROR: date/time field value out of range: "613566750"

6) Week number of year:
SELECT to_timestamp('2024 613566758 1', 'YYYY WW D');
to_timestamp
------------------------
2024-01-04 00:00:00+00
vs
SELECT to_timestamp('2024 61356675 1', 'YYYY WW D');
ERROR: date/time field value out of range: "2024 61356675 1"

7) ISO Week:
SELECT to_date('2024 613566758 1', 'IYYY IW ID');
to_date
------------
2024-01-04
vs
SELECT to_date('2024 61356675 1', 'IYYY IW ID');
to_date
---------------
1177946-01-28

Observed on REL_12_STABLE .. master.

(A couple of such anomalies were noticed at
https://www.postgresql.org/message-id/31ad2cd1-db94-bdb3-f91a-65ffdb4bef95%40gmail.com,
but as these ones trigger an incorrect behaviour even without -ftrapv and
in the back branches, maybe it's better to fix these defects separately.)