Shift of event types in v4.0

Broken API or pattern

All Event types extending IEvent explicitly or implicitly will be rewritten using the Listenable pattern. (Instead of function overrides with different event parameter literals, Listenable pattern uses record pattern where event names are keys.)
The impacted types use the naming convention I*Event whereas those using Listenable pattern do not have I prefix.

Known interfaces: IAgentSchedulerEvents, IAudienceEvents, ICheckoutEvents, IClientEvents, IConsensusOrderedCollectionEvents, IConsensusRegisterCollectionEvents, IContainerEvents, IContainerRuntimeBaseEvents, IContainerRuntimeEvents, IDeltaManagerEvents, IDeltaQueueEvents, IDirectoryEvents, IDocumentDeltaConnectionEvents, IDocumentServiceEvents, IDragDropEvents, IErrorEvent, IEvent, IFluidContainerEvents, IFluidDataStoreContextEvents, IFluidDataStoreRuntimeEvents, IFluidHandleEvents, ILocalFluidHandleEvents, IMigratorEvents, IOdspContainerServicesEvents, IOldestClientObservableEvents, IOldestClientObserverEvents, IQuorumClientsEvents, IQuorumProposalsEvents, ISequenceIntervalCollectionEvents, IServiceAudienceEvents, ISharedArrayEvents, ISharedCellEvents, ISharedCounterEvents, ISharedDirectoryEvents, ISharedMapEvents, ISharedMatrixEvents, ISharedObjectEvents, ISharedSegmentSequenceEvents, ISharedSignalEvents, ISharedTreeEvents, ISummarizerEvents, ISummaryCollectionOpEvents, ITaskManagerEvents, ITaskSubscriptionEvents

Preparation References

Use of EventEmitterWithErrorHandling, ExtendEventProvider, IEventProvider, IEventTransformer, TypedEventEmitter, and TypedEventTransform are likely to break if used with any custom types.

Migration recommendations to be provided.

Packages

@fluid-example/migration-tools, @fluid-experimental/oldest-client-observer, @fluid-experimental/tree, @fluidframework/agent-scheduler, @fluidframework/container-definitions, @fluidframework/container-runtime, @fluidframework/container-runtime-definitions, @fluidframework/core-interfaces, @fluidframework/counter, @fluidframework/datastore-definitions, @fluidframework/driver-definitions, @fluidframework/fluid-static, @fluidframework/legacy-dds, @fluidframework/map, @fluidframework/matrix, @fluidframework/odsp-client, @fluidframework/ordered-collection, @fluidframework/register-collection, @fluidframework/runtime-definitions, @fluidframework/sequence, @fluidframework/shared-object-base, @fluidframework/task-manager, fluid-framework

Expected Timeline

v4.0