refactor(informers): unify cache sync functions using generics

[ivankatliarchuk]

What does it do ?

• WaitForCacheSync and WaitForDynamicCacheSync unified into a single generic waitForCacheSync[K comparable] function.
• Changed from awkward "failed to sync %v: %w with timeout %s" to "failed to sync %v after %s: %w" - putting the timeout context before the wrapped error.
• Replaced wait.NeverStop with ctx.Done() for informer factories, allowing proper context-based cancellation
• line timeout := defaultRequestTimeout * time.Second noted the current timeout behavior for future consideration.

Something to consider for future.
Found this PR 60c649b#diff-cf68f602fa7c20e5341f3b83054df68ade1586a144b1eae5347e0ac47096d3aa

So in past it was something like

	// wait for the local cache to be populated.
	err = poll(time.Second, 60*time.Second, func() (bool, error) {
		return serviceInformer.Informer().HasSynced() &&
			endpointsInformer.Informer().HasSynced() &&
			podInformer.Informer().HasSynced() &&
			nodeInformer.Informer().HasSynced(), nil
	})
	if err != nil {
		return nil, fmt.Errorf("failed to sync cache: %v", err)

	}

It's basically very historycall.

What is wrong with current timeout := defaultRequestTimeout * time.Second Ignores the caller's context deadline: The function receives a ctx but then creates a new timeout, effectively overriding whatever deadline the caller may have set. If the caller passed a context with a 30s timeout, this function ignores it and waits 60s anyway.

As we supporint context correctly now #6049

We could remove internal timeout entirely - let caller control it. This needs testing

 func waitForCacheSync[K comparable](ctx context.Context, waitFunc func(<-chan struct{}) map[K]bool) error {
      for typ, done := range waitFunc(ctx.Done()) {
          if !done {
              return fmt.Errorf("failed to sync %v: %w", typ, ctx.Err())
          }
      }
      return nil
  }

Motivation

Close #6038

No more work is required for #6038, my understanind when this changes released kubernetes-sigs/gateway-api#4376 we should have al ready and fixed.

More

• Yes, this PR title follows Conventional Commits
• Yes, I added unit tests
• Yes, I updated end user documentation accordingly

[coveralls]

Pull Request Test Coverage Report for Build 20899119574

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 28 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.005%) to 78.973%

---

Files with Coverage Reduction	New Missed Lines	%
informers/informers.go	2	90.0%
gateway.go	26	85.98%

Totals
Change from base Build 20892650297:	0.005%
Covered Lines:	15955
Relevant Lines:	20203

---

💛 - Coveralls

[mloiseleur]

/lgtm

[ivankatliarchuk]

/approve

[k8s-ci-robot]

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