Fixes #25584

Motivation

OpenTelemetryProducerInterceptor had a deadlock:

1. eligible() returns tracer != null && propagator != null — both null after construction.
2. ProducerInterceptors.beforeSend() checks eligible() first, and skips the interceptor entirely if it returns false.
3. Tracer and propagator are initialized in beforeSend() via initializeIfNeeded(producer), which is never reached.

The interceptor was effectively a no-op — it never created any spans.

Modifications

Remove the lazy-initialization pattern and inject InstrumentProvider at construction time instead. The InstrumentProvider is already available in both ProducerBuilderImpl and ConsumerBuilderImpl where the interceptors are created:

• OpenTelemetryProducerInterceptor — accepts InstrumentProvider in constructor, initializes tracer and propagator eagerly. Removes initializeIfNeeded() and the initialized flag.
• OpenTelemetryConsumerInterceptor — same treatment for consistency.
• ProducerBuilderImpl / ConsumerBuilderImpl — pass client.instrumentProvider() to the constructor.

Verifying this change

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• Dependencies (add or upgrade a dependency)
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