AKS template cleanup

[CecileRobertMichon]

What type of PR is this?
/kind cleanup

What this PR does / why we need it:

• remove the multi-tenancy AKS flavor: the default for all clusters is to use multi-tenancy (AzureClusterIdentity), so the separate flavor is no longer relevant. In fact, the "aks" flavor is already using multi-tenancy.
• added a patch for the third agentpool to the test dir since it only meant for testing and should not be part of the AKS flavor we publish as a release asset
• removed the orphaned AAD AKS flavor which has no flavor directory (and is only showing a specific feature, since we want to get away from the "one feature, one flavor" model ref [docs/UX] should we reduce the number of flavors #1456)

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

Please confirm that if this PR changes any image versions, then that's the sole change this PR makes.

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

Removed aks-multi-tenancy flavor and the aks-aad flavors

[CecileRobertMichon]

/assign @jackfrancis

[CecileRobertMichon]

/retest

flake is known #2120

[CecileRobertMichon]

same issue

/retest

[jackfrancis]

What's the significance of this additional label?

[CecileRobertMichon]

it's what tells clusterctl to include the AzureClusterIdentity when moving a CAPZ cluster from one management cluster to another (clusterctl move). It's present in the other templates and was missing in this one https://github.com/kubernetes-sigs/cluster-api-provider-azure/blob/main/templates/cluster-template.yaml#L217

[jackfrancis]

/lgtm

[CecileRobertMichon]

/hold

for #1145

[CecileRobertMichon]

/hold cancel

rebased on top of #2095

[jackfrancis]

/lgtm

[k8s-ci-robot]

@CecileRobertMichon: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-cluster-api-provider-azure-ci-entrypoint	053d4db	link	false	/test pull-cluster-api-provider-azure-ci-entrypoint

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository. I understand the commands that are listed here.

[CecileRobertMichon]

/retest

"error"="failed to reconcile cluster services: failed to reconcile route table: failed to create resource capz-qadgta/capz-qadgta-node-routetable (service: routetables): network.RouteTablesClient#CreateOrUpdate: Failure sending request: StatusCode=0 -- Original Error: autorest/azure: Service returned an error. Status=<nil> Code=\"ResourceGroupBeingDeleted\" 

Looks like we had either a naming collision or something/someone deleted the RG out of band during the test

[CecileRobertMichon]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: CecileRobertMichon

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