dns: support AbortSignal in dns.lookup() and dns.promises.lookup()

[orgads]

Add a signal option to both dns.lookup() and dns.promises.lookup() that accepts an AbortSignal, allowing callers to cancel pending lookups.

When getaddrinfo blocks a libuv thread for an extended period (e.g. ~10s on EAI_AGAIN), new lookups queue behind the blocked threads and the number of unresolved promises grows without bound. Each pending promise holds references to the calling closure, preventing GC and causing a memory leak in long-running servers under sustained DNS failure.

With this change, callers can abort stale lookups:

  const ac = new AbortController();
  setTimeout(() => ac.abort(), 5000);
  await dns.promises.lookup(host, { signal: ac.signal });

If the signal is already aborted, the call rejects/calls back immediately without dispatching to libuv. If aborted while pending, the promise is rejected (or callback called) with an AbortError and the late oncomplete from libuv is silently ignored.

Fixes: #62503

[nodejs-github-bot]

Review requested:

• @nodejs/net

[codecov]

Codecov Report

❌ Patch coverage is 97.53086% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.71%. Comparing base (1ccae7c) to head (67e8f47).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
lib/dns.js	96.96%	1 Missing ⚠️
lib/internal/dns/promises.js	97.91%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #62528      +/-   ##
==========================================
- Coverage   89.72%   89.71%   -0.01%     
==========================================
  Files         695      695              
  Lines      214106   214175      +69     
  Branches    41002    41020      +18     
==========================================
+ Hits       192096   192157      +61     
+ Misses      14077    14070       -7     
- Partials     7933     7948      +15     

Files with missing lines	Coverage Δ
lib/dns.js	98.50% <96.96%> (-0.14%)	⬇️
lib/internal/dns/promises.js	98.20% <97.91%> (-0.09%)	⬇️

... and 47 files with indirect coverage changes

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