feat(eldritch): refactor dns to list and add CNAME support

[Cictrone]

Refactor dns library and add CNAME support

Overview

This PR refactors our newly introduced dns.list_a_records function to be more generic and extensible. The core method has been renamed to dns.list and now accepts an optional record_type parameter (capable of resolving "A" and "CNAME" records natively). To ensure code quality and testability, resolution logic within the std bindings has been separated into dedicated internal helper methods.

Key Changes

• API Redesign: Replaced the rigid dns.list_a_records with dns.list(domain, record_type='A', nameserver=None), enabling multi-type DNS probing.
• CNAME Support: Operators can now resolve CNAME records by invoking dns.list("domain.com", record_type="CNAME"). Defaults safely to IPv4 (A) if unspecified.
• Architectural Flow: Migrated the internal resolution logic from sweeping monolith functions into streamlined resolve_a_records() and resolve_cname_records() functions within std/mod.rs for readability and maintainability.
• Testing / Mock Adjustments: Extended DnsLibraryFake to appropriately handle assertions over both record types to guarantee mock-test coverage without breaking cargo check/WASM builds.
• Documentation: Overhauled docs/_docs/user-guide/eldritch.md to reflect dns.list along with functional snippet examples capturing the default and keyword invocation structures.

Testing

• Verified cargo test -p eldritch succeeds
• Checked cargo check -p eldritch-libdns
• Tested both A and CNAME return values in fake/std logic paths.

[github-actions]

Summary

Tests 📝	Passed ✅	Failed ❌	Skipped ⏭️	Other ❓	Flaky 🍂	Duration ⏱️
719	719	0	0	0	0	1ms

Previous Results

Build 🏗️	Result 🧪	Tests 📝	Passed ✅	Failed ❌	Skipped ⏭️	Other ❓	Flaky 🍂	Duration ⏱️
#1988	✅	719	719	0	0	0	0	41.6s

Insights

Average Tests per Run	Total Flaky Tests	Total Failed	Slowest Test (p95)
719	0	0	5.5s

Test Changes

0 test added, 0 removed

Slowest Tests

Test 📝	Results 📊	Duration (avg) ⏱️	Duration (p95) ⏱️
TestDockerExecutor_Build_ContextCancellation	1	5.5s	5.5s
TestInteractiveShell	1	5.1s	5.1s
TestOtherStreamOutput	1	5.0s	5.0s
TestDockerExecutor_Build_SimpleEcho	1	2.9s	2.9s
TestGetRandomName/NoDuplicates	1	1.5s	1.5s
TestGetRandomName	1	1.5s	1.5s
TestDockerExecutor_Build_StreamsOutputInRealTime	1	1.3s	1.3s
TestCreateTestData	1	1.3s	1.3s
TestAPI	1	1.1s	1.1s
TestTruncation	1	1.0s	1.0s

_{🎉 No failed tests in this run. | 🍂 No flaky tests in this run.}

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