fix: propagate async cancellation and await observer callbacks (#86) - #99

Change return type of method 'GetStreamsToSnapshot' from 'System.Collections.Generic.IEnumerable<NEventStore.Persistence.IStreamHead>' to 'NEventStore.Persistence.IStreamHead[]' for improved performance (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1859)

Change return type of method 'GetFrom' from 'System.Collections.Generic.IEnumerable<NEventStore.ICommit>' to 'NEventStore.ICommit[]' for improved performance (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1859)

Change return type of method 'GetFromTo' from 'System.Collections.Generic.IEnumerable<NEventStore.ICommit>' to 'NEventStore.ICommit[]' for improved performance (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1859)

Change return type of method 'DeleteStream' from 'System.Collections.Generic.IReadOnlyCollection<NEventStore.Persistence.InMemory.InMemoryPersistenceEngine.InMemoryCommit>' to 'NEventStore.Persistence.InMemory.InMemoryPersistenceEngine.InMemoryCommit[]' for improved performance (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1859)

Change return type of method 'Purge' from 'System.Collections.Generic.IReadOnlyCollection<NEventStore.Persistence.InMemory.InMemoryPersistenceEngine.InMemoryCommit>' to 'NEventStore.Persistence.InMemory.InMemoryPersistenceEngine.InMemoryCommit[]' for improved performance (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1859)

Change return type of method 'GetFrom' from 'System.Collections.Generic.IEnumerable<NEventStore.ICommit>' to 'NEventStore.ICommit[]' for improved performance (https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1859)

Non-nullable property 'Body' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.

Non-nullable property 'Payload' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.

Non-nullable property 'StreamId' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.

Non-nullable property 'BucketId' must contain a non-null value when exiting constructor. Consider adding the 'required' modifier or declaring the property as nullable.