Collector ingets input can receive non-unique `KeyValueList` keys from Windows event receiver payloads

Found a case in our repo where OTLP log body data contains a `kvlist_value` with non-unique keys:

`graylog2-server/src/test/resources/org/graylog/collectors/input/processor/windows-2025-eventlog-1.ndjson`

In the PowerShell events there, `event_data` contains multiple entries with `key: ""` (for example around `record_id=8526`). This shape is likely produced by the Windows event receiver for unnamed `EventData` elements.

That is problematic because OTLP `KeyValueList` is supposed to have unique keys. The proto/docs say:

- `KeyValueList`: “The keys MUST be unique”
- “The behavior of software that receives duplicated keys can be unpredictable”

Source:
`https://pkg.go.dev/go.opentelemetry.io/proto/otlp/common/v1`

This means any code that materializes such payloads into normal maps / JSON objects can silently lose data.