Add OpenLIT to Haystack Integrations

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How OpenLIT works with Haystack?

OpenLIT basically wraps around OpenAI, Anthropic etc functions and configures OpenTelemetry tracing and metrics for it. In the Haystack pipelines whenever the user runs a pipeline(Since Haystack also uses the same LLM functions), We are automatically able to wrap the pipeline (without needing to create any additional instrumentation for Haystack).

We did add instrumentation just for Document loaders as the rest of the pipeline can directly be tracked for reasons mentioned above.