Move sync / rollback method to the separate file

[Warashi]

What this PR does:

Move implementation of K8S_SYNC and K8S_ROLLBACK to separate files.

Why we need it:

To improve readability.

Which issue(s) this PR fixes:

Part of #4980

Does this PR introduce a user-facing change?: No

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

[codecov]

Codecov Report

Attention: Patch coverage is 40.22989% with 104 lines in your changes missing coverage. Please review.

Project coverage is 26.23%. Comparing base (025936b) to head (7a54aff).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...p/pipedv1/plugin/kubernetes/deployment/rollback.go	0.00%	60 Missing ⚠️
...g/app/pipedv1/plugin/kubernetes/deployment/sync.go	61.40%	34 Missing and 10 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5479      +/-   ##
==========================================
- Coverage   26.24%   26.23%   -0.01%     
==========================================
  Files         458      460       +2     
  Lines       49370    49370              
==========================================
- Hits        12956    12952       -4     
- Misses      35386    35389       +3     
- Partials     1028     1029       +1     

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[t-kikuc]

LGTM

more readable!

[khanhtc1202]

👍