docs(proposal): add docs for using cascading deletion

[CharlesQQ]

What type of PR is this?

What this PR does / why we need it:

Which issue(s) this PR fixes:
part of #4709

Special notes for your reviewer:

Does this PR introduce a user-facing change?:

NONE

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All modified and coverable lines are covered by tests ✅

Project coverage is 28.90%. Comparing base (c426e97) to head (788e44a).
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@@            Coverage Diff             @@
##           master    #5101      +/-   ##
==========================================
+ Coverage   28.19%   28.90%   +0.71%     
==========================================
  Files         631      632       +1     
  Lines       43482    43862     +380     
==========================================
+ Hits        12258    12680     +422     
+ Misses      30326    30267      -59     
- Partials      898      915      +17     

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unittests	28.90% <ø> (+0.71%)	⬆️

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[XiShanYongYe-Chang]

Thanks a lot @CharlesQQ

Hi, guys @RainbowMango @chaunceyjiang @whitewindmills @zhy76 @buji-code @lcw2
We can discuss here to improve the resource deletion policy.

[whitewindmills]

/assign

[whitewindmills]

does this annotation have a knock-on effect on dependent resources?―that is, one adds such an annotation to his Deployment, will the annotation affect its dependent resources(like ConfigMap)?

[XiShanYongYe-Chang]

Also ask @RainbowMango to help take a look.
/cc @RainbowMango

[XiShanYongYe-Chang]

/assign @RainbowMango

[chaosi-zju]

I didn't get what is the different below the title "Supported control plane resources".

[chaosi-zju]

I think we can highlight another comparison like solution one can set the orphan attribute at the granularity of each resource template, while solution two can only set the orphan` attribute at the granularity of policy. In 1 policy vs multi resource scene, we cann't execute orphan delete just by per resource.

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