feat: OTLP Sink Connector

### Description

Add a native OTLP (OpenTelemetry Protocol) sink connector for Apache Iggy using the opentelemetry-otlp Rust crate.

This connector will enable streams stored in Iggy to be exported to OpenTelemetry-compatible observability platforms such as Observe, Datadog, New Relic, Grafana Cloud, Honeycomb, Elastic, Splunk, and any backend supporting OTLP over gRPC or HTTP.

The OTLP sink is a foundational building block for positioning Iggy as a high-performance ingestion, buffering, replay, and routing layer for observability, AI telemetry, and event-driven architectures.

Connector Type: Sink Connector
---
Iggy Stream
↓
OTLP Sink
↓
OTLP Endpoint
---

Initial version:
- Logs

Future enhancements:
- Metrics
- Traces

===
Metrics
----
Expose connector metrics:
- otlp_sink_messages_sent_total
- otlp_sink_messages_failed_total
- otlp_sink_batches_sent_total
- otlp_sink_batch_latency_ms
- otlp_sink_retry_count_total

### Affected area / component

Connectors

### Proposed solution

_No response_

### Alternatives considered

_No response_

### Contribution

- [ ] I'm willing to submit a pull request to implement this feature

### Good first issue

- [x] I think this could be a good first issue for a new contributor

Start in the Connectors area by locating existing sink connectors and reviewing how they handle delivery, batching, retries, and connector metrics. Then read the opentelemetry-otlp Rust crate documentation and define the initial logs-only scope; done should include export to an OTLP endpoint over gRPC or HTTP and the listed sink metrics.

Written by the indexing model from the issue text.