[AKS] Allow updating primary agent pool name for load balancer config

[Liunardy]

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Related command

az aks loadbalancer update

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[Copilot]

Pull request overview

Enables az aks loadbalancer update to change the --primary-agent-pool-name for an existing load balancer configuration (previously rejected), and bumps the aks-preview extension version to publish the feature.

Changes:

• Allow primary_agent_pool_name changes in aks_loadbalancer_update_internal by treating it as an updatable field (instead of throwing BadRequestError).
• Add unit + scenario test coverage validating primary agent pool updates and “no changes requested” behavior.
• Bump extension version to 20.0.0b4 and document the change in HISTORY.rst.

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/aks-preview/azext_aks_preview/loadbalancerconfiguration.py	Removes the hard-block on changing primary_agent_pool_name and counts it as a valid update.
src/aks-preview/azext_aks_preview/tests/latest/test_loadbalancer_configuration.py	Adds unit tests covering primary agent pool updates + no-op update rejection.
src/aks-preview/azext_aks_preview/tests/latest/test_aks_commands.py	Extends the scenario test to validate updating primaryAgentPoolName end-to-end.
src/aks-preview/setup.py	Version bump to 20.0.0b4.
src/aks-preview/HISTORY.rst	Changelog entry for the new behavior and the release section for 20.0.0b4.

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[FumingZhang]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[FumingZhang]

lgtm

Queued live test to validate the change.

[FumingZhang]

lgtm

Queued live test to validate the change.

Test failed with error

          raise AzureInternalError(

                f"Timed out waiting for load balancers to reach 'Succeeded' state. "
                f"Operation took longer than {timeout_seconds} seconds."
            )

E azure.cli.core.azclierror.AzureInternalError: Timed out waiting for load balancers to reach 'Succeeded' state. Operation took longer than 600 seconds.

azure-cli-extensions/src/aks-preview/azext_aks_preview/loadbalancerconfiguration.py:344: AzureInternalError

https://dev.azure.com/msazure/CloudNativeCompute/CloudNativeCompute%20Team/_build/results?buildId=161615589&view=logs&j=b162b355-d59d-5864-ce0f-0a70f12dd28b&t=a26fe913-e2be-5062-b08e-d15f1acc7ea2&l=4335

Please also resolve merge conflict, cc @Liunardy

[Liunardy]

lgtm
Queued live test to validate the change.

Test failed with error

          raise AzureInternalError(

                f"Timed out waiting for load balancers to reach 'Succeeded' state. "
                f"Operation took longer than {timeout_seconds} seconds."
            )

E azure.cli.core.azclierror.AzureInternalError: Timed out waiting for load balancers to reach 'Succeeded' state. Operation took longer than 600 seconds.
azure-cli-extensions/src/aks-preview/azext_aks_preview/loadbalancerconfiguration.py:344: AzureInternalError

https://dev.azure.com/msazure/CloudNativeCompute/CloudNativeCompute%20Team/_build/results?buildId=161615589&view=logs&j=b162b355-d59d-5864-ce0f-0a70f12dd28b&t=a26fe913-e2be-5062-b08e-d15f1acc7ea2&l=4335

Please also resolve merge conflict, cc @Liunardy

Rebased and resolved merge conflict.
It failed at "Update the secondary LoadBalance with selectors" which is before the step that test the new change in this PR (update primary agent pool). I tested live again locally and there is no failure. cc @FumingZhang

[FumingZhang]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 2 pipeline(s).

[FumingZhang]

Re-queued live test