Refactor k8s plugin logic

[ffjlabo]

What this PR does:

as title

fixes

• Split logic for each stages 9d7b059, 2fc980d
• Remove type Stage 1fd132b

Why we need it:

We want to implement plugins with SDK.

Which issue(s) this PR fixes:

Part of #4980 #5006

Does this PR introduce a user-facing change?:

• How are users affected by this change:
• Is this breaking change:
• How to migrate (if breaking change):

[codecov]

Codecov Report

Attention: Patch coverage is 37.62887% with 121 lines in your changes missing coverage. Please review.

Project coverage is 25.66%. Comparing base (57c48c1) to head (e4b3347).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...p/pipedv1/plugin/kubernetes/deployment/rollback.go	0.00%	71 Missing ⚠️
...g/app/pipedv1/plugin/kubernetes/deployment/sync.go	59.13%	37 Missing and 10 partials ⚠️
...app/pipedv1/plugin/kubernetes/deployment/plugin.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5678      +/-   ##
==========================================
- Coverage   25.66%   25.66%   -0.01%     
==========================================
  Files         474      476       +2     
  Lines       50905    50894      -11     
==========================================
- Hits        13066    13063       -3     
+ Misses      36848    36841       -7     
+ Partials      991      990       -1     

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[Warashi]

Thank you