Support to_char on timestamptz

[neverchanje]

Is your feature request related to a problem? Please describe.

select to_char(now(), 'YYYY-MM-DD HH24:MI:SS.MS TZ');

This query fails with the following error:

ERROR:  QueryError: Feature is not yet implemented: ToChar[Timestamptz, unknown]
Tracking issue: https://github.com/risingwavelabs/risingwave/issues/112

to_char ( timestamp, text ) → text is supported:

dev=> select to_char(now()::timestamp, 'YYYY-MM-DD HH24:MI:SS.MS TZ');
NOTICE:  Your session timezone is UTC. It was used in the interpretation of timestamps and dates in your query. If this is unintended, change your timezone to match that of your data's with `set timezone = [timezone]` or rewrite your query with an explicit timezone conversion, e.g. with `AT TIME ZONE`.

          to_char
---------------------------
 2023-02-06 05:04:17.MS TZ
(1 row)

to_char ( timestamp with time zone, text ) → text is not.

Describe the solution you'd like

Converts time stamp to string according to the given format.

• to_char(timestamptz '2002-04-20 17:31:12.66', 'HH12:MI:SS') → 05:31:12

Describe alternatives you've considered

No response

Additional context

Sqllogictest:

query T
SELECT to_char(TIMESTAMPTZ '1997-02-03 11:12:59.9', 'YYYY-MM-DD HH24:MI:SS.MS TZ')
----
1997-02-03 11:12:59.900 UTC

query T
SELECT to_char(TIMESTAMPTZ '1997-02-03 11:12:59.7777', 'YYYY-MM-DD HH24:MI:SS.MS TZ')
----
1997-02-03 11:12:59.777 UTC

[TennyZhuang]

#7334