add nodepool controoller unit test

[luc99hen]

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line:
/kind bug
/kind documentation

/kind enhancement

/kind good-first-issue
/kind feature
/kind question
/kind design
/sig ai
/sig iot
/sig network
/sig storage
/sig storage

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes # #73

Special notes for your reviewer:

This PR add unit tests for nodepool controller and some related utils function. To improve the test coverage, some controller code are refactored for better testability.

Does this PR introduce a user-facing change?

no

other Note

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In response to this:

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespace from that line:
/kind bug
/kind documentation
/kind enhancement
/kind good-first-issue
/kind feature
/kind question
/kind design
/sig ai
/sig iot
/sig network
/sig storage
/sig storage

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes # #73

Special notes for your reviewer:

This PR add unit tests for nodepool controller and some related utils function. To improve the test coverage, some controller code are refactored for better testability.

Does this PR introduce a user-facing change?

other Note

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[luc99hen]

/assign @kadisi

[codecov]

Codecov Report

Merging #89 (d09f5c4) into master (fe8491b) will increase coverage by 7.57%.
The diff coverage is 72.00%.

@@            Coverage Diff             @@
##           master      #89      +/-   ##
==========================================
+ Coverage    7.78%   15.36%   +7.57%     
==========================================
  Files          17       18       +1     
  Lines        1901     1953      +52     
==========================================
+ Hits          148      300     +152     
+ Misses       1724     1617     -107     
- Partials       29       36       +7     

Flag	Coverage Δ
unittests	15.36% <72.00%> (+7.57%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...r/controller/nodepool/nodepool_enqueue_handlers.go	0.00% <ø> (ø)
...manager/controller/nodepool/nodepool_controller.go	56.41% <71.62%> (+39.58%)	⬆️
...g/yurtappmanager/util/gate/custom_resource_gate.go	70.83% <100.00%> (ø)

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[rambohe-ch]

/lgtm
/approve

[openyurt-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: luc99hen, rambohe-ch

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