text: Title: Feature: add `broker.ping()` method
  Body: We should add a mechanism to check real connection to broker liveness as a step of #1181 impl
  
  First of all, we should add abstract method to [`BrokerUsecase` class](https://github.com/airtai/faststream/blob/main/faststream/broker/core/usecase.py#L48)
  
  Then we should add this method impl to **KafkaBroker**/**RabbitBroker**/etc (using `self._connection` or `self._producer` object)
  
  Also, we should add tests for that functional smth there: https://github.com/airtai/faststream/blob/main/tests/brokers/base/connection.py