[INLONG-16070][SDK] Fix potential block in Golang SDK

[gunli]

Fixes #10670

Motivation

There is a potential block bug in the Golang SDK:
In the callback of conn.AsyncWrite() we may call worker.updateConn(), updateConn() may try to open new conn in some case, if so, it will call gnet.Client.Dial(), but gnet.Client.Dial() will be blocked unitl gnet event loop mark the conn is opened, but now the event loop is running in conn.AsyncWrite()'s callback:
conn.AsyncWrite()'s callback-->worker.updateConn()-->gnet.Client.Dial()-->waiting for conn.AsyncWrite()'s callback to return.

Modifications

1. update conn async in the conn.AsyncWrite() callback;
2. update conn async when conn is closed.

Verifying this change

(Please pick either of the following options)

• This change is a trivial rework/code cleanup without any test coverage.

• This change is already covered by existing tests, such as:
  (please describe tests)

• This change added tests and can be verified as follows:

  (example:)

  • Added integration tests for end-to-end deployment with large payloads (10MB)
  • Extended integration test for recovery after broker failure

Documentation

• Does this pull request introduce a new feature? (no)
• If yes, how is the feature documented? (not applicable / docs / JavaDocs / not documented)
• If a feature is not applicable for documentation, explain why?
• If a feature is not documented yet in this PR, please create a follow-up issue for adding the documentation