add cluster flags for karmadactl top pod

[zhzhuang-zju]

What type of PR is this?
/kind feature

What this PR does / why we need it:
add cluster flags for karmadactl top pod

Which issue(s) this PR fixes:
Parts of #4217

Special notes for your reviewer:
Extracted some public methods for subsequent implementation of the top node command

Add cluster flags to query the resource status of the cluster pod. Like
➜ karmada git:(top) ✗ karmadactl top po -Cmember1
NAME CLUSTER CPU(cores) MEMORY(bytes)
mycurlpods member1 0m 1Mi

Does this PR introduce a user-facing change?:

`karmadactl`: Introduced `--cluster` flag to `top` command to specify the cluster name.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (c3c3766) 52.83% compared to head (bdb1451) 52.82%.
Report is 16 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4223      +/-   ##
==========================================
- Coverage   52.83%   52.82%   -0.01%     
==========================================
  Files         239      240       +1     
  Lines       23558    23595      +37     
==========================================
+ Hits        12447    12465      +18     
- Misses      10434    10454      +20     
+ Partials      677      676       -1     

Flag	Coverage Δ
unittests	52.82% <100.00%> (-0.01%)	⬇️

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[jwcesign]

/lgtm

Can you help add the corresponding e2e?

[zhzhuang-zju]

/lgtm

Can you help add the corresponding e2e?

Thx~, I added the e2e task when decomposing tasks in the issue #4217

[chaunceyjiang]

Nice work~

/lgtm

[RainbowMango]

/approve

@chaunceyjiang I'm surprised you are not on the approver list.
Now we lack approvers on CLI things, would you like to take the role?

[karmada-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: RainbowMango

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• pkg/karmadactl/OWNERS [RainbowMango]

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[chaunceyjiang]

Now we lack approvers on CLI things, would you like to take the role?

Yes. ❤️