Zero-ETL support for PostgreSQL

[TianyuZhang1214]

• Snapshot Synchronization: Start by implementing issue Load from pg_dump #130. If this approach doesn't meet performance requirements, consider DuckDB PostgreSQL Extension (recommended by @VWagen1989 ). Here is a code example:

-- All SQLs need to be executed one by one.

INSTALL postgres_scanner;
LOAD postgres_scanner;
ATTACH 'dbname=postgres user=postgres password=root host=127.0.0.1 port=15432' AS pg_postgres (TYPE POSTGRES);

BEGIN;
COPY FROM DATABASE pg_postgres TO postgres;
--  store the result into a variable of code(go, shell).
SELECT * FROM postgres_query('pg_postgres', 'SELECT pg_current_wal_lsn()');
COMMIT;

• Delta Synchronization: Schedule this task after PR feat: add initial support for postgresql replication #141 is completed.