operator: fix the issue that the default values of Karmada are not correctly applied

[zhzhuang-zju]

What type of PR is this?
/kind bug

What this PR does / why we need it:
When the operator reconciles the Karmada CR, it will first validate the Karmada CR and then set the default values. This causes the validation to fail when users omit the configuration of certain fields.

It is necessary to set the default values first and then perform the validation.

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:
How to reproduce it:

1. deploy karmada-operator

$ hack/deploy-karmada-operator.sh {path/to/kubeconfig} {context}

2. deploy a karmada CR

$ kubectl apply -v=4 -f - <<EOF
apiVersion: operator.karmada.io/v1alpha1
kind: Karmada
metadata:
  name: karmada-demo
  namespace: test
spec:
  components:
    karmadaDescheduler: {}
    etcd: {}
EOF

3. view operator log

E0224 11:56:27.802480       1 controller.go:96] Validation failed for karmada: validation errors: [spec.components.etcd: Invalid value: v1alpha1.Etcd{Local:(*v1alpha1.LocalEtcd)(nil), External:(*v1alpha1.ExternalEtcd)(nil)}: unexpected empty etcd configuration]

Does this PR introduce a user-facing change?:

`karmada-operator`: fix the error of validation failure when some fields of the Karmada CR are not configured. 

[XiShanYongYe-Chang]

Can the update operation also be placed before validateKarmada?

[zhzhuang-zju]

The update operation should only be carried out when the validation is passed
The update operation, you mean controllerutil.AddFinalizer?

[XiShanYongYe-Chang]

I'm not sure if it's appropriate. Can this update be placed before validate?

karmada/operator/pkg/controller/karmada/controller.go

Lines 136 to 141 in 006cf70

	updated := controllerutil.AddFinalizer(karmada, ControllerFinalizerName)
	if _, isExist := karmada.Labels[DisableCascadingDeletionLabel]; !isExist {
	labelMap := labels.Merge(karmada.GetLabels(), labels.Set{DisableCascadingDeletionLabel: "false"})
	karmada.SetLabels(labelMap)
	updated = true
	}

[zhzhuang-zju]

I'm not sure if it's appropriate. Can this update be placed before validate?

@XiShanYongYe-Chang updated, does it meet your expectations?

[XiShanYongYe-Chang]

Thanks~
/lgtm

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Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 48.07%. Comparing base (cfebd4d) to head (df7f007).
Report is 10 commits behind head on master.

Files with missing lines	Patch %	Lines
operator/pkg/controller/karmada/controller.go	0.00%	4 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6158      +/-   ##
==========================================
- Coverage   48.10%   48.07%   -0.03%     
==========================================
  Files         668      668              
  Lines       55316    55327      +11     
==========================================
- Hits        26608    26598      -10     
- Misses      26973    26991      +18     
- Partials     1735     1738       +3     

Flag	Coverage Δ
unittests	48.07% <0.00%> (-0.03%)	⬇️

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[RainbowMango]

/lgtm
/approve

[karmada-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: RainbowMango

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