fix: capture Run() error in metrics controller goroutine

[abhaygoudannavar]

What this PR does

Fixes a closure bug where the metrics controller goroutine logged the wrong error on failure.

Problem

In main.go (lines 280-285), the goroutine that runs the metrics controller never captures the return value of metricsController.Run(). Instead, it references the outer err variable from the metrics.NewController() call:

metricsController, err := metrics.NewController(kruisegameInformerFactory)
if err != nil {
    setupLog.Error(err, "unable to create metrics controller")
    os.Exit(1)
}
kruisegameInformerFactory.Start(signal.Done())
go func() {
    if metricsController.Run(signal) != nil {
        setupLog.Error(err, "unable to setup metrics controller")  // wrong err
        os.Exit(1)
    }
}()

Since NewController succeeded (otherwise we'd have exited), err is nil by the time the goroutine runs. So if Run() fails, the log prints a nil error — making the failure impossible to diagnose.

Fix
Capture the return value of Run() into its own variable:

    if runErr := metricsController.Run(signal); runErr != nil {
        setupLog.Error(runErr, "unable to setup metrics controller")
        os.Exit(1)
    }
}()

fixes #325

[kruise-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please assign furykerry for approval by writing /assign @furykerry in a comment. For more information see:The Kubernetes Code Review Process.

The full list of commands accepted by this bot can be found here.

Details

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 40.76%. Comparing base (206e756) to head (a19f1df).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #330   +/-   ##
=======================================
  Coverage   40.76%   40.76%           
=======================================
  Files         112      112           
  Lines       12544    12544           
=======================================
  Hits         5114     5114           
  Misses       7019     7019           
  Partials      411      411           

Flag	Coverage Δ
unittests	40.76% <ø> (ø)

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

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[abhaygoudannavar]

hey @furykerry can you check out on this pr?
if there are any changes required