[Event Hubs] Add live tests for consumer receive options

## Summary

The consumer tests run with the default `prefetch` value. They set `receive_timeout` but do not assert its semantics. The `with_instance_id` builder option has no live coverage on either the consumer or the producer.

## Motivation

Prefetch controls the credit that the receiver grants to the link, so a wrong value can stall a stream or waste memory. The receive timeout controls what happens when a partition is idle. The instance id appears in service side diagnostics. .NET live-tests all three. Part of #4886.

## Proposal

- [ ] Read with a custom `prefetch` value, and read again with a very small `prefetch` value (.NET `ConsumerCanReadBatchOfEventsWithCustomPrefetchAndBatchCounts`, `ConsumerCanReadEventsWithPrefetchDisabled`).
- [ ] Assert the `receive_timeout` semantics. The stream must yield within the timeout when the partition is idle (.NET `ConsumerRespectsTheWaitTimeWhenReading`).
- [ ] Open clients with `with_instance_id` and make sure that operations succeed (.NET `ConsumerWithAnIdentifierCanReadEvents`, `ProducerWithIdentifierCanSend`).

## Validation

Deploy the test resources with `eng/common/TestResources/New-TestResources.ps1 -ServiceDirectory eventhubs`. Set `EVENTHUBS_HOST` and `EVENTHUB_NAME`. Then run `AZURE_TEST_MODE=live cargo test --package azure_messaging_eventhubs --test '*'`. Each new test passes in live mode.