feat(logs): preserve field order from VictoriaLogs response

[arturminchukov]

Related issue: #563

Describe Your Changes

• Serialize log fields via fastjson Del + MarshalTo instead of a Go map, so the labels JSON keeps VL's field order instead of an alphabetical sort
• Stop parsing _stream into fields (VL already expands stream labels as top-level fields); keep the raw _stream string for the stable log id
• Remove the now-unused orderedLabels type and pkg/utils/stream_fields_parser
• Update test fixtures to real VL top-level expansion; drop invalid_stream case

Checklist

The following checks are mandatory:

• My change adheres to VictoriaMetrics contributing guidelines.
• My change adheres to VictoriaMetrics development goals.

---

Summary by cubic

Preserves VictoriaLogs field order in labels JSON and stops parsing _stream. Builds stable log IDs from raw _time, _msg, and _stream_id bytes (keyed on _stream_id) to match VL responses and improve stability (#563).

• Refactors
  • Serialize labels with fastjson (Del unwanted fields, then MarshalTo) so log fields keep VL order; _stream/_stream_id are kept as-is.
  • Split responses and tests into response_logs.go, response_stats.go, response_hits.go; keep shared types/error parsers/labelsToJSON in response.go.
  • Remove pkg/utils/stream_fields_parser; update fixtures and drop pkg/plugin/test-data/invalid_stream.

^{Written for commit e0db154. Summary will update on new commits.}

[arturminchukov]

Removed stream parsing, cause stream labels always exist in the log as separate labels, so we don't need to parse them manually.

[cubic-dev-ai]

No issues found across 14 files

_{Re-trigger cubic}

[dmitryk-dk]

As for me we shouldn't change tests files because those are real cases which was fixed via the real users issue.
If we just need to leave _stream fields we can update only this logic and tests related to it

[hagen1778]

It would be nice to refactor datasource_test.go in future. I think it is too verbose and repetetive - that's the reason why it got so many changes in this PR

[arturminchukov]

1st commit:

• Split the response.go into response_logs.go, response_stats.go, and response_hist.go with their tests without any changes in functionality.

2-nd commit:

• removed parsing _stream field.
• changed function buildLogID - now it requires byte arguments and changed _stream field to _stream_id field.
• fixed tests according to missing parse stream functionality (just removed unnecessary test, and fixed those tests that expected parsing _stream field)

@dmitryk-dk @hagen1778 Could you please review it again?

[hagen1778]

LGTM

[dmitryk-dk]

Overall looks good!
One thing what i do not like is that we removed from the tests the real test case
but if you sure it is expected than ok

_, err := w.Write([]byte(`{"_time":"2024-02-20", "_stream":"{application=\"logs-benchmark-Apache.log-1708437847\",hostname=}"}`))
			if err != nil {
				t.Fatalf("error write reposne: %s", err)
			}

[arturminchukov]

Overall looks good! One thing what i do not like is that we removed from the tests the real test case but if you sure it is expected than ok

_, err := w.Write([]byte(`{"_time":"2024-02-20", "_stream":"{application=\"logs-benchmark-Apache.log-1708437847\",hostname=}"}`))
			if err != nil {
				t.Fatalf("error write reposne: %s", err)
			}

I removed this test case, cause I removed the parsing _stream field, so this test case is no longer relevant.