remove c++ based node internal dns module

[anonrig]

rust-backed-dns autogate has been fully rolled out.

[ask-bonk]

I'm Bonk, and I've done a quick review of your PR.

This PR removes the C++ DnsUtil class and its autogate guard, unconditionally using the Rust JSG-native DNS implementation.

Findings (ranked by severity):

1. [MEDIUM] Stale //src/rust/dns dependency in node-core BUILD target — src/workerd/api/node/BUILD.bazel:78 still has //src/rust/dns in implementation_deps, but the only consumer (dns.c++) was deleted. The crate itself (src/rust/dns/lib.rs line 1) says: "This file is a somewhat duplicate of src/rust/api/dns.rs, and will be removed once autogate is unnecessary." That time is now. Remove the dep line and consider deleting src/rust/dns/ entirely.

2. [LOW] Stale include in node.h — src/workerd/api/node/node.h:21 still includes <workerd/util/autogate.h> but no longer references any autogate types after this change. Can be removed.

3. [LOW] Dead autogate entry — RUST_BACKED_NODE_DNS in src/workerd/util/autogate.h:32 and src/workerd/util/autogate.c++:28-29 has no remaining callers. Consider removing it in this PR or a follow-up.

This review was generated by an AI assistant and may contain inaccuracies.

[ask-bonk]

Review posted successfully on PR #6298. Here's a summary of the findings:

1. [MEDIUM] Stale //src/rust/dns dependency in node-core BUILD target — the only consumer (dns.c++) was deleted, and the crate itself says it's a duplicate pending removal.
2. [LOW] Stale #include <workerd/util/autogate.h> in node.h — no longer used after removing autogate checks.
3. [LOW] Dead RUST_BACKED_NODE_DNS autogate entry in autogate.h and autogate.c++ — no remaining callers.

github run

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.63%. Comparing base (e3e9c1c) to head (c1c10ac).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6298      +/-   ##
==========================================
- Coverage   70.64%   70.63%   -0.02%     
==========================================
  Files         420      418       -2     
  Lines      111649   111564      -85     
  Branches    18368    18368              
==========================================
- Hits        78880    78801      -79     
+ Misses      21800    21794       -6     
  Partials    10969    10969              

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[fhanau]

optional, non-blocking: I assume the autogate itself will be removed in a follow-up?

[anonrig]

optional, non-blocking: I assume the autogate itself will be removed in a follow-up?

Yes!