Support TIMESTAMP_NS, TIMESTAMP_MS & TIMESTAMP_S

[destrex271]

Draft PR to support TIMESTAMP_NS, TIMESTAMP_MS & TIMESTAMP_S types available in duckdb in postgres.

Fixes #283

[destrex271]

Insert statements executed from postgres on tables in motherduck are working as expected for TIMESTAMP_MS & TIMESTAMP_S.

-- Tables created in Motherduck
CREATE TABLE timestamps_ms_tbl(a timestamp_ms);
CREATE TABLE timestamps_s_tbl(a timestamp_s);
-- ------------------------------------------------------------------------

-- Insert statements executed from postgres
INSERT INTO timestamps_ms_tbl VALUES('1992-12-12 12:12:12.1989898'::TIMESTAMP);
INSERT INTO timestamps_s_tbl VALUES('1992-12-12 12:12:12.1989898'::TIMESTAMP);

-- Selecting Data from mother duck via postgres
-- -------------------------------------------------------------------
SELECT * FROM timestamps_ms_tbl; 
-- Output:
-- 1992-12-12 12:12:12.198

SELECT * FROM timestamps_s_tbl;
-- Output
-- 1992-12-12 12:12:12

Currently working on converting TIMESTAMP_MS selected from duckdb into Postgres TIMESTAMP type

[destrex271]

@JelteF, I tested this against some tables in Motherduck, but I’m not sure how to go about writing regression tests for this. From what I understand, the type_support tests are queries run from within PostgreSQL. Since this PR doesn’t add any new types to Postgres, I’m a bit confused about the best way to proceed.

[destrex271]

Also unrelated to this issue, I noticed another problem while working on this:

As you can see, for some reason on motherduck timestamp_ns is being compressed to timestamp with micro second precision only.