{AKS} Stabilize AKS live test scenarios

[FumingZhang]

🤖 PR Validation — ️✔️ All clear

Breaking Changes	Tests
️✔️ None	️✔️ 130/130

Related command

az aks

Description

Harden AKS live tests against the failure modes observed in CLI Runner:

• Normalize quoted-empty service principal environment values and skip credential-dependent scenarios when credentials are unavailable.
• Poll non-terminal cluster and agent-pool responses, then re-fetch exact cluster/agent-pool resources through native aks show commands before running checks.
• Retry only the known transient AKS serialization conflicts (Another operation is in progress and PutExtensionAddonHandler.PUT) with bounded exponential backoff. Other errors and expected-failure scenarios still fail immediately.
• Preserve feature-required regions for zone, Automatic SKU, Azure Container Storage, LocalDNS, and network-isolated tests instead of applying the runner-wide region override.
• Select currently supported non-LTS Kubernetes versions for LocalDNS and network-isolated live tests.
• Explicitly set the IPv4 managed outbound IP count in the dual-stack scenario.
• Skip obsolete Basic Load Balancer scenarios because Basic LB retired on September 30, 2025.

Current dev also contains the newer AKS SDK/API version that resolves the maintenance and artifact-streaming payload mismatches seen in the original run. Azure Monitor LRO poller leaks are handled separately by #33734.

This PR changes test infrastructure only; customer-facing command behavior is unchanged.

Testing Guide

python -m pytest -q \
  src/azure-cli/azure/cli/command_modules/acs/tests/latest/test_aks_provisioning_retry.py \
  src/azure-cli/azure/cli/command_modules/acs/tests/latest/test_custom_preparers.py

Result: 27 passed, 7 subtests passed.

Focused scenario replay validation:

2 passed, 6 skipped

The skips are the intentionally live-only or retired scenarios. All changed files also pass python -m py_compile and git diff --check.

History Notes

None (test infrastructure only).

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