Base on PR#3415, this PR further fix some other known issues of the AKS PR check-in test pipeline. The main changes are as follows:

• Update az_aks_tool, add path check to avoid unexpected errors caused by invalid path
• Fix the problem that the variable passed to az_aks_tool in the extensions test script is lost
• Add two new test cases excluded by default (test_aks_disable_local_accounts, test_aks_update_to_msi_cluster_with_addons)
• Add a new pipeline variable EXT_TEST_MATRIX to override the default filtering rules

General Guidelines

• Have you run azdev style <YOUR_EXT> locally? (pip install azdev required)
• Have you run python scripts/ci/test_index.py -q locally?

For new extensions:

• My extension description/summary conforms to the Extension Summary Guidelines.

About Extension Publish

There is a pipeline to automatically build, upload and publish extension wheels.
Once your PR is merged into master branch, a new PR will be created to update src/index.json automatically.
The precondition is to put your code inside this repo and upgrade the version in the PR but do not modify src/index.json.