[Improve][SDK] Avoid calling endpoint update handlers while holding the lock in the Dataproxy Go SDK discoverers

[yfsn666]

Description

In the Dataproxy Go SDK, if an OnEndpointUpdate handler calls back into AddEventHandler/DelEventHandler/GetEndpoints from within the Manager-based or DNS discoverer's lookup, the same goroutine re-enters the discoverer's RWMutex and deadlocks.

InLong Component

InLong SDK

Are you willing to submit PR?

• Yes, I am willing to submit a PR!

Code of Conduct

• I agree to follow this project's Code of Conduct