[Mocha] Cancel message handlers and release interrupted messages on shutdown

[tobias-tengler]

When a receive endpoint stopped, in-flight handlers were never cancelled because ReceiveContext discarded the transport's cancellation token, so they kept running after shutdown began. Stopping also left PostgreSQL messages behind. A handler that finished after the stop began could not delete its message, because the delete used the already cancelled token, and messages that were leased but not finished stayed locked until the 5 minute lease timeout. Both were then redelivered and processed a second time. Finally, a transport or endpoint that failed to stop kept the remaining ones from stopping.

This PR passes the endpoint's cancellation token to handlers, including batch handlers, and keeps shutdown cancellation from triggering retries, fault handling or error logs. RabbitMQ and Azure Service Bus settle messages with CancellationToken.None, so an interrupted message is still nacked or abandoned. Batches are collected and processed per receive endpoint, so stopping one endpoint only cancels its own batches, and MaxConcurrentBatches now applies per endpoint.

The PostgreSQL endpoint deletes or releases a handled message with CancellationToken.None. When polling is cancelled, it releases the messages of the current batch that it still holds, so they are redelivered right away instead of after the lease timeout.

MessagingRuntime.StopAsync and MessagingTransport.StopAsync keep stopping the remaining transports and endpoints when one fails, then rethrow the first failure. A transport that failed to stop stays started, so disposing the runtime tries it again before the consumers are disposed.

[github-actions]

Patch coverage

88.7% of changed lines covered (197/222)

File	Covered	Changed	Patch %
…/Middlewares/Receive/RabbitMQAcknowledgementMiddleware.cs	1	2	50.0% 🔴
src/Mocha/src/Mocha/Transport/MessagingTransport.cs	16	23	69.6% 🔴
…/src/Mocha.Transport.Postgres/PostgresReceiveEndpoint.cs	32	37	86.5% 🟡
…/Mocha/src/Mocha/Consumers/Implementations/BatchConsumer.cs	82	93	88.2% 🟡
src/Mocha/src/Mocha/Consumers/Batching/BatchCollector.cs	15	16	93.8% 🟡
…/Receive/AzureServiceBusAcknowledgementMiddleware.cs	2	2	100.0% 🟢
…/src/Mocha.Transport.InMemory/InMemoryReceiveEndpoint.cs	3	3	100.0% 🟢
…/Mocha.Transport.Postgres/Connection/PostgresMessageStore.cs	23	23	100.0% 🟢
…/Connection/RabbitMQConsumerManager.cs	1	1	100.0% 🟢
src/Mocha/src/Mocha/Endpoints/ReceiveEndpoint.cs	2	2	100.0% 🟢
…/Mocha/src/Mocha/Middlewares/Consume/Retry/RetryExecutor.cs	2	2	100.0% 🟢
…/src/Mocha/Middlewares/Receive/ReceiveDeadLetterMiddleware.cs	1	1	100.0% 🟢
…/src/Mocha/Middlewares/Receive/ReceiveFaultMiddleware.cs	1	1	100.0% 🟢
…/Receive/Redelivery/ReceiveRedeliveryMiddleware.cs	1	1	100.0% 🟢
src/Mocha/src/Mocha/Middlewares/ReceiveContext.cs	1	1	100.0% 🟢
src/Mocha/src/Mocha/Runtime/MessagingRuntime.cs	13	13	100.0% 🟢
src/Mocha/src/Mocha/ThrowHelper.cs	1	1	100.0% 🟢

Uncovered changed lines (JSON)

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Project coverage: 58.6% (314284/536564 lines)