[beatreceiver] Remove ES exporter specific attributes present in otelconsumer with kafka/logstash output

Currently, we add ES exporter specific attributes to otelconsumer.
1. `elasticsearch.ingest_pipeline` in log records [code](https://github.com/elastic/beats/blob/main/x-pack/libbeat/outputs/otelconsumer/otelconsumer.go#L129-L133)
2. And `elastic.mapping.mode` in scope attributes [code](https://github.com/elastic/beats/blob/main/x-pack/libbeat/outputs/otelconsumer/otelconsumer.go#L93)

They must be stripped when using kafka/logstash output as these are not required in the context of non-elasticsearch backend.

For more context see https://github.com/elastic/beats/pull/48494#discussion_r2717559221

Start in x-pack/libbeat/outputs/otelconsumer/otelconsumer.go at the referenced lines 93 and 129-133, and review the discussion in PR 48494. Trace how the Kafka and Logstash output paths handle scope and log-record attributes, then verify that elastic.mapping.mode and elasticsearch.ingest_pipeline are stripped there while the issue’s non-Elasticsearch behavior is satisfied.

Written by the indexing model from the issue text.