[Improve][SDK] Support configuring request timeout in the DataProxy Go SDK discoverer

### Description

In the Dataproxy Go SDK, the discoverer's HTTP requests to the Manager have no timeout configured, so they can hang indefinitely when the Manager is slow or unreachable.

### InLong Component

InLong SDK

### Are you willing to submit PR?

- [x] Yes, I am willing to submit a PR!

### Code of Conduct

- [x] I agree to follow this project's [Code of Conduct](https://www.apache.org/foundation/policies/conduct)

Locate the DataProxy Go SDK discoverer and trace the HTTP requests it sends to the Manager. Check how request configuration is handled, then verify that a configured timeout is applied and that slow or unreachable Manager requests no longer hang indefinitely.

Written by the indexing model from the issue text.