GH-985: InMemoryDocumentStore implements IEventStore

[jeremydmiller]

Closes #985. Part of #955.

The in-memory prototyping store now implements IEventStore<IInMemoryDocumentSession, IInMemoryQuerySession>, and AddInMemoryStoreForPrototyping registers it as IEventStore. Store-agnostic helpers written against IEventStore (Bobcat's CritterStack layer, services.EventStore()) now work on a stub-first app instead of throwing "No JasperFx.Events.IEventStore is registered".

What the issue asked for, mapped to the change:

• Opening a session: AllDatabases() returns one InMemoryEventDatabase, and OpenSession(database[, tenantId]) opens a lightweight session.
• OpenReadOnlyEventStore() returns a query session's Events, which now also implements IReadOnlyEventStore:
  • FetchStreamAsync was already there.
  • QueryEventsAsync(EventQuery) supports every filter except tags (DCB). Tag filters throw rather than being ignored. Paging uses long arithmetic, so PageSize = int.MaxValue is safe.
  • QueryStreamStates() is LINQ-to-objects and works with the shared async terminators.
  • Because it's also the session's IQueryEventStore, AggregateStreamAsync<T> works directly, the same as on Marten.
• Session Events: already IEventOperations + IQueryEventStore.
• Projection waits: projections run inline, so WaitForNonStaleProjectionDataAsync returns immediately and AllShards() / AllProjectionProgress() are empty.
• Out of scope: the daemon, subscriptions, compaction and dead letters throw NotSupportedException with the store's usual "switch to Marten, Polecat or Fisher" message.

The compliance fixture's EventStore now returns the store. I didn't enroll EventQueryCompliance or StreamStateQueryCompliance: they register tag types and archive or compact streams, which this store doesn't support. Instead, InMemoryIEventStoreTests has 9 facts that only use the IEventStore contract, along the same path Bobcat takes.

Tests

• EventStoreTests: 286 passed, 22 skipped, on net9.0 and net10.0
• InMemoryEventStoreTests: 117 passed, 7 skipped (all async-daemon facts, same as before)

Follow-up: add an in-memory lane to WolverineFx.Bobcat's tests once this ships.

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