Handle `partial_success` in OTLP Logs export responses

Spec requirement

On an otherwise-2xx response, ExportLogsServiceResponse.partial_success (rejected_log_records, error_message) SHOULD be handled/logged. This is the same defect class this repo already tracks for other signals (ex. issue #1361, 'Handle partial success responses from OTLP export services').

Current behavior

exporter/otlp-logs/lib/opentelemetry/exporter/otlp/logs/logs_exporter.rb:172-175 (permalink) reads and discards the response body on Net::HTTPSuccess without ever decoding it as Opentelemetry::Proto::Collector::Logs::V1::ExportLogsServiceResponse — the partial_success field (present in the generated protobuf) is never inspected.

Suggested fix

Decode the response body on success, and if partial_success.rejected_log_records > 0, log partial_success.error_message via OpenTelemetry.handle_error, matching the existing log_status pattern already used on the error path (:241-251) (permalink).

Related rows in SPEC_COMPLIANCE_LOGS.md

OTLP-13

Start in exporter/otlp-logs/lib/opentelemetry/exporter/otlp/logs/logs_exporter.rb, especially the successful-response handling at lines 172-175 and the log_status pattern at lines 241-251. Check the generated ExportLogsServiceResponse fields and the OTLP-13 row in SPEC_COMPLIANCE_LOGS.md. Done means successful responses inspect partial_success and rejected records are reported through OpenTelemetry.handle_error.