otel: fix drop handling in insert

[alltilla]

No description provided.

[bazsi]

This looks good, I was just wondering when can it happen that our formatter returns false?

[alltilla]

It fails if some of the .otel. or .otel_raw. fields are wrong, for example if the .otel.metric.data.type is not one of the valid values (gauge, sum, histogram, expontential_histogram or sum). This should not happen when we receive (and parse) with the opentelemetry() driver, only if a user tries to set those manually and makes an error. The processing of the OTel messages is very forgiving, we do partial formatting and parsing everywhere, so we can process incoming messages that lack mandatory fields, and we can create messages similarly.

[MrAnno]

In case of a real insert() failure, we should clear logs_service_request to avoid duplication as the threaded dest driver reinserts the discarded batch.

Currently, there is no such case, so I guess we're good.