[improve][pulsar-proxy] Update proxy lookup throw exception type

[tuteng]

Fixes #

Master Issue: #

Motivation

Currently most of the exceptions after proxy lookup throw service not ready, but some clients do not handle this exception, when the user encounters an authentication error, the client will receive the serviceNotReady exception, which makes the user confused
So use getServerError to wrap the exception to avoid always throwing serviceNotReady exception when encountering an exception

Modifications

Use getServerError to wrap the exception to avoid always throwing serviceNotReady exception when encountering an exception

Verifying this change

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

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

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This change added tests and can be verified as follows:

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

Does this pull request potentially affect one of the following parts:

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• Dependencies (add or upgrade a dependency)
• The public API
• The schema
• The default values of configurations
• The binary protocol
• The REST endpoints
• The admin CLI options
• Anything that affects deployment

Documentation

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  This is some unusual optimization, which does not require a change in the documentation

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[nodece]

Looks good to me.