feat: introducing a karmadactl top command

[chaunceyjiang]

What type of PR is this?
/kind feature

What this PR does / why we need it:

The difference between kubectl and karmadactl lies in the fact that karmadactl has introduced a new column called "Cluster", which allows you to view the resource usage of pods in different clusters.

Please see more details.

#3578 (comment)

Which issue(s) this PR fixes:
Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

`karmadactl`: Introduced `top` command.

[chaunceyjiang]

[codecov-commenter]

Codecov Report

Merging #3593 (62482f4) into master (25db1e0) will decrease coverage by 0.02%.
Report is 2 commits behind head on master.
The diff coverage is n/a.

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@@            Coverage Diff             @@
##           master    #3593      +/-   ##
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- Coverage   54.71%   54.69%   -0.02%     
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  Files         229      229              
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- Hits        12077    12074       -3     
- Misses       9351     9354       +3     
  Partials      646      646              

Flag	Coverage Δ
unittests	54.69% <ø> (-0.02%)	⬇️

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see 1 file with indirect coverage changes

[chaunceyjiang]

[chaunceyjiang]

/cc @carlory @lonelyCZ Please take a look.

[jwcesign]

Can we push it forward?

[chaunceyjiang]

/cc @jwcesign PTAL.

[jwcesign]

/lgtm

[chaunceyjiang]

/cc @RainbowMango @carlory @lonelyCZ

[RainbowMango]

/assign

[RainbowMango]

Looks great! Just some nits.

karmadactl has introduced a new column called "Cluster",

Two questions on that:

1. I see the Cluster is present as the first column, have you ever considered putting it right after the pod name? Just like karmadactl get:

# karmadactl get pods -A 
NAMESPACE            NAME                                            CLUSTER   READY   STATUS    RESTARTS       AGE
kube-system          coredns-5d78c9869d-f98rf                        member1   1/1     Running   0              5d4h
kube-system          coredns-5d78c9869d-j9znc                        member1   1/1     Running   0              5d4h

2. Is the output sorted by default? I think it would be better to sort it first by cluster and then by resource name.

[chaunceyjiang]

Is the output sorted by default?

Default Sorting

1. Sort by cluster name
2. Sort by resource namespace
3. Sort by resource name

[chaunceyjiang]

[chaunceyjiang]

/cc @RainbowMango Updated.

[RainbowMango]

/lgtm
/approve
Thanks.

[karmada-bot]

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