feat(packetloss): add option to enable DNS resolution in MTR tests

[s0up4200]

Summary

• Adds mtr_enable_dns config option to the [packetloss] section that controls whether MTR tests resolve hostnames or show raw IP addresses
• Disabled by default to preserve current behavior (fast, numeric-only output)
• When enabled, removes --no-dns (Unix) / -n (Windows) flags from MTR commands so hostnames like one.one.one.one are shown instead of 1.1.1.1
• Configurable via config file (mtr_enable_dns = true) or environment variable (NETRONOME__PACKETLOSS_MTR_ENABLE_DNS=true)

Closes #160

Test plan

• go build ./... compiles without errors
• go test ./... all tests pass
• Start with mtr_enable_dns = false (default) and verify MTR results show IP addresses only
• Start with mtr_enable_dns = true and verify MTR results show resolved hostnames
• Set NETRONOME__PACKETLOSS_MTR_ENABLE_DNS=true env var and verify it overrides the config file
• Run generate-config and verify the new option appears in the generated config

Summary by CodeRabbit

• New Features
  • Added configuration option to control DNS lookup behavior during packet loss monitoring tests, allowing users to toggle DNS resolution checks during network diagnostics.

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[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds a new mtr_enable_dns configuration option to allow users to enable DNS resolution in MTR tests. The flag is integrated through the configuration system, passed to the PacketLossService, and conditionally applied to MTR argument building on both Unix and Windows platforms.

Changes

Cohort / File(s)	Summary
Configuration Schema config.toml, internal/config/config.go	Introduces new mtr_enable_dns boolean field (default: false) to PacketLossConfig with TOML tag mtr_enable_dns and environment variable PACKETLOSS_MTR_ENABLE_DNS. Updated configuration initialization and serialization to support the new option.
Service Initialization cmd/netronome/main.go, internal/speedtest/packetloss.go	PacketLossService constructor now accepts enableDNS boolean parameter. Service constructor call in main.go passes cfg.PacketLoss.MTREnableDNS when initializing the service. New field added to PacketLossService struct to store the flag.
MTR Argument Building internal/speedtest/mtr_unix.go, internal/speedtest/mtr_windows.go	Updated buildMTRArgs function signatures on both platforms to accept enableDNS parameter. Changed conditional logic: --no-dns (Unix) and -n (Windows) flags are now only appended when DNS is disabled, rather than being unconditionally included.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐰 A config flag hops through the code,
DNS names now show the network road,
Hostnames glow where IPs once stood,
MTR sees the path—oh, so good! ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: adding a DNS resolution option to MTR tests for packet loss monitoring.
Linked Issues check	✅ Passed	The implementation fully addresses issue #160 by adding mtr_enable_dns config option with both file and environment variable support, and properly controls DNS behavior in MTR.
Out of Scope Changes check	✅ Passed	All changes are directly related to implementing the MTR DNS resolution feature requested in issue #160; no unrelated modifications detected.
Docstring Coverage	✅ Passed	Docstring coverage is 80.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing touches

• 📝 Generate docstrings

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