Handle telemetry MAC lookup failures when network interfaces are unavailable

[Copilot]

CLI startup could fail in telemetry initialization when MAC address retrieval falls back to NetworkInterface.GetAllNetworkInterfaces() on systems where netlink sockets are unavailable. In that environment, NetworkInformationException escaped and crashed commands like dotnet --version.

• Telemetry machine ID fallback hardening

  • Updated TelemetryCommonProperties.GetMachineId() to catch NetworkInformationException from MAC lookup and fall back to a generated GUID instead of allowing process-terminating initialization failure.
  • This keeps telemetry best-effort while preserving CLI command execution in constrained environments.

• Targeted regression coverage

  • Added a telemetry test that injects a NetworkInformationException from getMACAddress and verifies both machine ID fields continue to be produced as GUIDs via fallback behavior.

private string GetMachineId()
{
    try
    {
        return _getMACAddress() is { } macAddress ? _hasher(macAddress) : Guid.NewGuid().ToString();
    }
    catch (NetworkInformationException)
    {
        return Guid.NewGuid().ToString();
    }
}

[dotnet-policy-service]

This PR has been labeled with Area-Telemetry. Please ensure that any telemetry changes in this PR

• comply with the published guidance * are added to the repo-local telemetry documentation * get a matching .NET Docs issue raised to document the telemetry changes
  • Go to https://learn.microsoft.com/dotnet/core/tools/telemetry
  • Scroll down to the bottom and click the 'Open a documentation issue' link to create an issue with pre-filled details

[marcpopMSFT]

Fix looks reasonable to me. We already have fallback logic. This just explicitly catches the network exception and uses the same fallback logic to produce an ID.

[Copilot]

Pull request overview

This PR hardens CLI telemetry initialization so MAC address lookup failures from unavailable network interfaces do not crash CLI startup. It keeps machine ID telemetry best-effort by falling back to generated GUIDs.

Changes:

• Catches NetworkInformationException during telemetry machine ID generation.
• Adds regression coverage for MAC lookup throwing NetworkInformationException.

Reviewed changes

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

File	Description
src/Cli/dotnet/Telemetry/TelemetryCommonProperties.cs	Adds fallback handling for network information failures during machine ID generation.
test/dotnet.Tests/TelemetryTests/TelemetryCommonPropertiesTests.cs	Adds a targeted test validating GUID fallback behavior when MAC lookup throws.