fix(host_metrics source): add defensive check to prevent panics

[pront]

Summary

Check the input to NativeEndian::read_u32 since the latter can panic.

Change Type

• Bug fix
• New feature
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

How did you test this PR?

On an ubuntu 24.04 instance with:

api:
  enabled: true

sources:
  my_source_id:
    type: host_metrics
    scrape_interval_secs: 30

sinks:
  console:
    inputs: [ "my_source_id" ]
    type: console
    encoding:
      codec: json
      json:
        pretty: true

Does this PR include user facing changes?

• Yes. Please add a changelog fragment based on our guidelines.
• No. A maintainer will apply the "no-changelog" label to this PR.

Checklist

• Please read our Vector contributor resources.
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    • cargo clippy --workspace --all-targets -- -D warnings
    • cargo nextest run --workspace (alternatively, you can run cargo test --all)
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References

Ref #22057

[pront]

This is the fix.

[pront]

Moved this to a helper function

[datadog-vectordotdev]

Datadog Report

Branch report: pront/host-metrics-tcp-avoid-panic
Commit report: 62d5ab0
Test service: vector

✅ 0 Failed, 7 Passed, 0 Skipped, 25.47s Total Time