[metrics] OpenTelemetry metric reporter

### Search before asking

- [X] I searched in the [issues](https://github.com/alibaba/fluss/issues) and found nothing similar.

### Motivation

*Note: Low priority feature (created for tracking purposes)*

[OpenTelemetry Observability Primer](https://opentelemetry.io/docs/concepts/observability-primer/)

Fluss observability capabilities are currently limited to _vendor-specific_ formats (e.g., metrics are exposed via Prometheus).

Adding an OpenTelemetry metric reporter allows users to choose their preferred observability backend and facilitates Fluss usage on Kubernetes.

### Solution

- Add a metric reporter for OpenTelemetry
- Create a quickstart guide that shows how to get up and running incl. ingesting logs into OpenTelemetry ([resource 1](https://opentelemetry.io/blog/2024/collecting-otel-compliant-java-logs-from-files/), [resource 2](https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/main/instrumentation/log4j/log4j-appender-2.17/library/README.md))

### Willingness to contribute

- [X] I'm willing to submit a PR!