Support multiple hosts in provider configuration

[ljluestc]

When a comma-separated list of hosts is provided in the host field (e.g., host1,host2), the provider will now attempt to connect to each host in sequence until a successful connection is established or the timeout is reached.

Changes

• postgresql/proxy_driver.go: Updated the custom proxyDriver to intercept connection attempts.
  • Added parseAddress helper to handle comma-separated hosts and IPv6 addresses.
  • Modified DialTimeout to iterate through the list of hosts.
• postgresql/proxy_driver_test.go: Added unit tests to verify address parsing logic for various formats (single host, multiple hosts, IPv6).