ignore AKS user-assigned ClientID/PrincipalID in diff

[nojnhuh]

What type of PR is this?
/kind bug

What this PR does / why we need it: This fixes a bug causing an endless reconciliation of AzureManagedControlPlane with spec.identity.type set to UserAssigned because of a continuous diff like this:

&armcontainerservice.ManagedCluster{
  	Location:         nil,
  	ExtendedLocation: nil,
  	Identity: &armcontainerservice.ManagedClusterIdentity{
  		DelegatedResources: nil,
  		Type:               &"UserAssigned",
  		UserAssignedIdentities: map[string]*armcontainerservice.ManagedServiceIdentityUserAssignedIdentitiesValue{
  			"/subscriptions/<sub>/resourcegroups/<group>/providers/Microsoft.ManagedIdentity/userAssignedIdentities/<name>": &{
- 				ClientID:    nil,
+ 				ClientID:    &"00000000-0000-0000-00000-00000000000",
- 				PrincipalID: nil,
+ 				PrincipalID: &"00000000-0000-0000-00000-00000000000",
  			},
  		},
  		PrincipalID: nil,
  		TenantID:    nil,
  	},
  	Properties: &{AutoScalerProfile: &{}, IdentityProfile: {"kubeletidentity": &{ResourceID: &"/subscriptions/<sub>/resourcegrou"...}}, KubernetesVersion: &"1.26.3", NetworkProfile: &{}, ...},
  	SKU:        &{Name: &"Base", Tier: &"Free"},
  	... // 5 identical fields
  }

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:

• cherry-pick candidate <-- I'm guessing the SDK v1 implementation on the release branches has the same bug.

TODOs:

• squashed commits
• includes documentation
• adds unit tests

Release note:

Fixed a bug causing AzureManagedControlPlanes with `spec.identity.type` set to `UserAssigned` to needlessly reconcile constantly.

[CecileRobertMichon]

/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 6930a10862232875232ce0742919b6a66dfe1dfe

[CecileRobertMichon]

/cherry-pick release-1.10

[k8s-infra-cherrypick-robot]

@CecileRobertMichon: once the present PR merges, I will cherry-pick it on top of release-1.10 in a new PR and assign it to you.

In response to this:

/cherry-pick release-1.10

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.

[mboersma]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: mboersma

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• OWNERS [mboersma]

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[codecov]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.13% 🎉

Comparison is base (803f6dd) 56.04% compared to head (3a924b6) 56.17%.
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3962      +/-   ##
==========================================
+ Coverage   56.04%   56.17%   +0.13%     
==========================================
  Files         190      190              
  Lines       19480    19450      -30     
==========================================
+ Hits        10917    10926       +9     
+ Misses       7939     7899      -40     
- Partials      624      625       +1     

Files Changed	Coverage Δ
azure/services/managedclusters/spec.go	51.22% <100.00%> (+0.72%)	⬆️

... and 6 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[k8s-infra-cherrypick-robot]

@CecileRobertMichon: #3962 failed to apply on top of branch "release-1.10":

Applying: ignore AKS user-assigned ClientID/PrincipalID in diff
Using index info to reconstruct a base tree...
M	azure/services/managedclusters/spec.go
M	azure/services/managedclusters/spec_test.go
Falling back to patching base and 3-way merge...
Auto-merging azure/services/managedclusters/spec_test.go
CONFLICT (content): Merge conflict in azure/services/managedclusters/spec_test.go
Auto-merging azure/services/managedclusters/spec.go
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 ignore AKS user-assigned ClientID/PrincipalID in diff
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

In response to this:

/cherry-pick release-1.10

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.

[nojnhuh]

@CecileRobertMichon: #3962 failed to apply on top of branch "release-1.10":

#3963