Refactor pkg test helper functions

[kevindiu]

Description:

This PR refactor pkg/agent/handler test implementation.
The changes and the discussion is as the following link:
#1675

Related Issue:

How Has This Been Tested?:

Environment:

• Go Version: 1.18.2
• Docker Version: 20.10.8
• Kubernetes Version: 1.22.0
• NGT Version: 1.14.5

Types of changes:

• Bug fix [type/bug]
• New feature [type/feature]
• Add tests [type/test]
• Security related changes [type/security]
• Add documents [type/documentation]
• Refactoring [type/refactoring]
• Update dependencies [type/dependency]
• Update benchmarks and performances [type/bench]
• Update CI [type/ci]

Changes to Core Features:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your core changes, as applicable?
• Have you successfully ran tests with your changes locally?

Checklist:

• I have read the CONTRIBUTING document.
• I have checked open Pull Requests for the similar feature or fixes?
• I have added tests and benchmarks to cover my changes.
• I have ensured all new and existing tests passed.
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation accordingly.

[vdaas-ci]

[CHATOPS:HELP] ChatOps commands.

• 🙆‍♀️ /approve - approve
• 💌 /changelog - replace the PR body by changelog details
• 🍱 /format - format codes and add licenses
• ✅ /gen-test - generate test codes
• 🏷️ /label - add labels
• ⏪ /rebase - rebase master
• 🔚 2️⃣ 🔚 /label actions/e2e-deploy - run E2E deploy & integration test

[codecov]

Codecov Report

Merging #1678 (c477b85) into master (815b44a) will increase coverage by 0.21%.
The diff coverage is 89.77%.

@@            Coverage Diff             @@
##           master    #1678      +/-   ##
==========================================
+ Coverage   31.16%   31.37%   +0.21%     
==========================================
  Files         372      374       +2     
  Lines       32503    32591      +88     
==========================================
+ Hits        10130    10226      +96     
+ Misses      21993    21984       -9     
- Partials      380      381       +1     

Impacted Files	Coverage Δ
internal/test/data/vector/gen.go	93.40% <77.77%> (-6.60%)	⬇️
internal/test/data/request/insert.go	92.10% <92.10%> (ø)
internal/conv/conv.go	76.66% <100.00%> (+11.66%)	⬆️
internal/test/data/request/object.go	100.00% <100.00%> (ø)
pkg/agent/core/ngt/service/option.go	89.57% <0.00%> (-1.85%)	⬇️
internal/worker/queue.go	98.73% <0.00%> (-1.27%)	⬇️
internal/worker/worker.go	84.37% <0.00%> (+0.78%)	⬆️
...nt/core/ngt/service/vqueue/uninserted_index_map.go	78.68% <0.00%> (+5.46%)	⬆️
...ent/core/ngt/service/vqueue/undeleted_index_map.go	76.66% <0.00%> (+5.55%)	⬆️

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[kevindiu]

/format

[vdaas-ci]

[FORMAT] Updating license headers and formatting go codes triggered by kevindiu.