[4.18] MCG Bucket Notifications - add advanced tests, improvements and fixes

[sagihirshfeld]

This PR adds the following tests to test_bucket_notifications.py:

1. test_multi_notif_event_types: check that other operations besides PutObject result in the expected notificaitons
2. test_multiple_bucket_notifs_setups: verify that MCG can handle bucket notifications configurations, where different buckets are each sending notifications to a separate Kafka topic.
3. test_bucket_notifs_shared_topic: test that multiple buckets can send their notifications to the same Kafka topic

Additionally, the following fixes were made:

• A typo error in delete_object_tags
• Skip decorators have been added to the TestBucketNotifications class. Any deployment that might have an issue with external networking have been skipped because setting up Kafka requires such access.
• Typos in test_bucket_notifications.py
• The polarion IDs of test_bucket_notifications[default-logs-pvc] and test_bucket_notifications[provided-logs-pvc]

And finally, the following improvements/additions have been made:

• The costly health checks in BucketNotificationsManager::add_notif_conn_to_noobaa_cr has been replaced by a simpler one from a static method from the MCG class.
• An option to skip the wait/health check in BucketNotificationsManager::add_notif_conn_to_noobaa_cr and BucketNotificationsManager::put_bucket_notification have been added.
• Exception handling has been improved at test_bucket_notifications to show what events are missing from the notifications.
• The function-scoped add_env_vars_to_noobaa_core fixture have been added to conftest.py

[openshift-ci]

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