Support OTLP as output in the logging plugin

[nickytd]

What would you like to be added:
Support otlp in the plugin output.

Why is this needed:
Today the plugin only ships logs to vali enabled backend using the valitail plugin. However to successfully migrate the backends to OpenTelemetry we need also to be able tp ship the logs to an otlp enabled backend (either otel-collector or any other backend supporting otlp) Until the backend migration is fully completed, the plugin needs to support both valitail and otlp outputs.

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