Call disconnect on protocol when reconnecting in Replication connection

[DohanKim]

Problems

• When the ReplicationConnection encounters a socket error, it reconnects to another socket without properly closing the current one (similar to call disconnect on protocol when reconnecting in simple connection #717).
• When the ReplicationConnection fails to establish a connection, it doesn’t log any errors and simply retries indefinitely.

Worst Case Scenario

If Postgres terminates a replication connection process due to an OOM issue or a network error:

• Postgrex creates a new ReplicationConnection without closing the previous one.
• This repeats up to 10 times. (with auto_reconnect option)
• The max_wal_senders limit (default: 10) is reached, preventing new ReplicationConnection from being created.
• The system enters a silent infinite loop of reconnecting without any logs.

This issue has occurred in my production app during periods of network instability.

Commit Changes

• Invoke disconnect on the protocol when reconnecting to a ReplicationConnection.
• Log an error message when a ReplicationConnection fails to establish a connection.

[josevalim]

Can you please also add this exception to SImpleConnection for consistency?

[DohanKim]

Added

[josevalim]

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