fix(cluster): remove raleted metrics label when cluster is deleted

[CharlesQQ]

What type of PR is this?
/kind bug

What this PR does / why we need it:

Which issue(s) this PR fixes:
Fixes #5843

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

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[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 12.50000% with 14 lines in your changes missing coverage. Please review.

Project coverage is 46.28%. Comparing base (88c3e44) to head (bd68ef8).
Report is 38 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/metrics/cluster.go	0.00%	11 Missing ⚠️
pkg/controllers/cluster/cluster_controller.go	40.00%	2 Missing and 1 partial ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5866      +/-   ##
==========================================
+ Coverage   46.20%   46.28%   +0.07%     
==========================================
  Files         663      663              
  Lines       54580    54777     +197     
==========================================
+ Hits        25218    25352     +134     
- Misses      27739    27796      +57     
- Partials     1623     1629       +6     

Flag	Coverage Δ
unittests	46.28% <12.50%> (+0.07%)	⬆️

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[RainbowMango]

Have you tested it? Can you share the metrics before and after cluster is deleted?

[RainbowMango]

What if the removeCluster raises an error? Do we still clean up the metrics?

[CharlesQQ]

What if the removeCluster raises an error? Do we still clean up the metrics?

shouldn't clean up the metrics, I'll fix it!

[CharlesQQ]

Have you tested it? Can you share the metrics before and after cluster is deleted?

yes, I join a cluster named host

Before metrics: following metrics not removed after host deleted from karmada

cluster_ready_node_number{cluster_name="host"} 0
cluster_ready_state{cluster_name="host"} 1
cluster_sync_status_duration_seconds_bucket{cluster_name="host",le="0.005"} 0
cluster_sync_status_duration_seconds_bucket{cluster_name="host",le="0.01"} 0
cluster_sync_status_duration_seconds_bucket{cluster_name="host",le="0.025"} 0
cluster_sync_status_duration_seconds_bucket{cluster_name="host",le="0.05"} 1
cluster_sync_status_duration_seconds_bucket{cluster_name="host",le="0.1"} 3
cluster_sync_status_duration_seconds_bucket{cluster_name="host",le="0.25"} 3
cluster_sync_status_duration_seconds_bucket{cluster_name="host",le="0.5"} 4
cluster_sync_status_duration_seconds_bucket{cluster_name="host",le="1"} 4
cluster_sync_status_duration_seconds_bucket{cluster_name="host",le="2.5"} 4
cluster_sync_status_duration_seconds_bucket{cluster_name="host",le="5"} 4
cluster_sync_status_duration_seconds_bucket{cluster_name="host",le="10"} 4
cluster_sync_status_duration_seconds_bucket{cluster_name="host",le="+Inf"} 4
cluster_sync_status_duration_seconds_sum{cluster_name="host"} 0.667916613
cluster_sync_status_duration_seconds_count{cluster_name="host"} 4

After: metrics removed successfully.