Tracer.addSpanLink should take two contexts

[lmolkova]

azure-sdk-for-java/sdk/eventhubs/azure-messaging-eventhubs/src/main/java/com/azure/messaging/eventhubs/EventHubProducerAsyncClient.java

Lines 551 to 553 in 9e44afc

	// TODO (lmolkova) we need better addSpanLinks(Context shared, Context link)
	Object eventSpanContext = event.getContext().getData(SPAN_CONTEXT_KEY).orElse(Context.NONE);
	tracerProvider.addSpanLinks(sharedContext.addData(SPAN_CONTEXT_KEY, eventSpanContext));

When we add a link to the span, we have two independent contexts:

• shared context to start Send or Process span
• individual message contexts

Currently, we have to merge two contexts, but it's not efficient and not correct.
We need an api on tracer that would take two Contexts like addSpanLink(Context shared, Context link)

[lmolkova]

Required for #30557