* See the issue #1862
Adding an event when ManagedMqttClient actually subscribe/unsubscribe to topics.
This event has to be used in parallel with connected event to know the exact state.
* Rename SubscriptionsResultAsync to SubscriptionsChangedAsync.
* Rename internal field for event
* Update ReleaseNotes.md
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Co-authored-by: Pierre Dufrene <pierre.dufrene@se.com>
Co-authored-by: Christian <6939810+chkr1011@users.noreply.github.com>
