fix: handle mixed endpoints in DNS clusters

[avinxshKD]

What type of PR is this?

/kind bug

What this PR does / why we need it:

Fixes DNS cluster rewriting for mixed hostname and IP endpoints. The old code replaced only the last hostname and panicked for localities containing only IP endpoints.

The new logic expands each hostname independently while preserving existing IP endpoints and locality order. Added regression coverage for mixed endpoints and multiple hostnames.

Which issue(s) this PR fixes:

Fixes #1848

Special notes for your reviewer:

The change is limited to overwriteDnsCluster. Existing IPv4-only behavior is preserved.

Does this PR introduce a user-facing change?:

Yes.

Fix kernel-native DNS cluster resolution for localities containing mixed hostname and IP endpoints.

[gemini-code-assist]

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[kmesh-bot]

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Details

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• pkg/controller/OWNERS

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[Copilot]

Pull request overview

Fixes a panic and incorrect DNS endpoint rewriting in kernel-native ADS DNS handling when clusters contain localities with mixed hostname and IP endpoints. The updated overwriteDnsCluster logic now expands each hostname endpoint independently while preserving existing IP endpoints and maintaining per-locality endpoint ordering.

Changes:

• Reworked overwriteDnsCluster to rebuild each locality’s LbEndpoints by expanding each hostname into its resolved IP endpoints and preserving IP/non-socket endpoints.
• Removed debug/unused logic (fmt.Printf, slices.Replace) tied to the prior “replace last hostname” approach.
• Added a regression test covering mixed hostname/IP endpoints across multiple localities and multiple hostnames in-order.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
pkg/controller/ads/dns.go	Rebuilds locality endpoints to safely expand hostnames and preserve IP endpoints without panics.
pkg/controller/ads/dns_test.go	Adds regression coverage for mixed endpoints and multiple hostnames across localities.

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[codecov]

Codecov Report

❌ Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 39.50%. Comparing base (63e0279) to head (ec11cbe).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/controller/ads/dns.go	88.88%	1 Missing ⚠️

Files with missing lines	Coverage Δ
pkg/controller/ads/dns.go	70.05% <88.88%> (-0.95%)	⬇️

... and 2 files with indirect coverage changes

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