refactor: Use new URL for connection string parsing

[denghongcai]

This commit refactors the connection URL parsing logic in src/index.js to use the new URL() constructor. This change provides a more robust and standardized way to parse connection strings, addressing several limitations of the previous implementation:

• IPv6 Support: The new parsing logic correctly handles IPv6 addresses in connection strings.
• Encoded Password Handling: Usernames and passwords with special characters that have been URL-encoded are now correctly decoded.

To achieve this, the parseUrl function was rewritten to replace the postgres:// or postgresql:// protocol with http:// before passing the string to the URL constructor. This allows the use of the standard URL parsing mechanism for a custom protocol.

Additionally, two new helper functions, parseHost and parsePort, have been introduced to correctly extract host and port information from various formats, including single-host, multi-host, and IPv6 addresses.

[porsager]

Can you add tests so that we can see where the old logic is failing and also the new logic fixing it?