OpenTelemetry-Go: BatchProcessor can busy-spin when export buffer is full

### Summary A `BatchingProcessor` in `go.opentelemetry.io/otel/sdk/log` can enter a tight CPU loop when the asynchronous export buffer is full. Under exporter backpressure, attacker-driven high-volume log emission can keep the queue at or above the batch size, causing repeated immediate export retries and a denial of service through CPU exhaustion. Introduced in commit: 4af9c20 ### Details `NewBatchingProcessor` wraps the exporter with `newBufferExporter(exporter, 1)` (`sdk/log/batch.go:116-122`), so the asynchronous export input can fill quickly when the downstream exporter blocks. The poll goroutine dequeues a batch with `b.q.TryDequeue`, calls `b.exporter.EnqueueExport(r)`, and then immediately sends on `b.pollTrigger` whenever `qLen >= b.batchSize` (`sdk/log/batch.go:129-165`). `bufferExporter.EnqueueExport` is non-blocking: it sends to `e.input` if possible and returns `false` in the `default` case when the channel is full (`sdk/log/exporter.go:221-248`). `TryDequeue` leaves `q.len` unchanged when the write callback returns `false` (`sdk/log/batch.go:289-314`). Therefore, while the exporter is backpressured, `EnqueueExport` fails, the queue remains at or above one full batch, and the poll loop continuously retriggers itself without waiting for the ticker. ### PoC [validation-artifact.zip](https://github.com/user-attachments/files/27494002/validation-artifact.zip) The validation artifact contains a PoC bundle: - `validation-artifact.tar:main.go`: PoC source. - `validation