Update to use Ginkgo BDD testing framework to align with the exist test style

[xiaoyu74]

What type of PR is this?

(unit-test)

What this PR does / Why we need it?

Updated to use Ginkgo BDD testing framework for my healthcheck subcommand to align with the current test style

Which Jira/Github issue(s) does this PR fix?

Resolves #

Special notes for your reviewer

• The main logic of the merged healthcheck subcommand is not change but just refactored the test cases using the Ginkgo BDD framework
• Changed the struct name (e.g below) based on the naming convention

// Default implementations
type DefaultNetworkInterfaceImpl struct{}

type DefaultHTTPClientImpl struct {
        Client *http.Client
}

• CheckBackplaneAPIConnectivity function is not covered by the test case since it's just call the existing CheckAPIConnection() which defined in the existing config.GetBackplaneConfiguration.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 31.25000% with 33 lines in your changes missing coverage. Please review.

Project coverage is 44.65%. Comparing base (74599c8) to head (5125f75).
Report is 8 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #487      +/-   ##
==========================================
- Coverage   45.78%   44.65%   -1.13%     
==========================================
  Files          82       82              
  Lines        6199     6427     +228     
==========================================
+ Hits         2838     2870      +32     
- Misses       3011     3203     +192     
- Partials      350      354       +4     

Files	Coverage Δ
pkg/healthcheck/check_proxy.go	72.34% <100.00%> (+35.75%)	⬆️
pkg/healthcheck/check_vpn.go	72.97% <100.00%> (ø)
pkg/healthcheck/connectivity_checks.go	8.43% <8.33%> (-2.24%)	⬇️

... and 5 files with indirect coverage changes

[samanthajayasinghe]

/lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: samanthajayasinghe, xiaoyu74

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[openshift-ci]

@xiaoyu74: all tests passed!

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