Resolve state <-> state-test-utils circular dependency (#16093)

* Resolve state <-> state-test-utils circular dependency

* Fix type errors

libs/state-internal/src/default-single-user-state.ts

@@ -0,0 +1,38 @@
+import { Observable, combineLatest, of } from "rxjs";
+
+import { LogService } from "@bitwarden/logging";
+import {
+  CombinedState,
+  SingleUserState,
+  StateEventRegistrarService,
+  UserKeyDefinition,
+} from "@bitwarden/state";
+import { AbstractStorageService, ObservableStorageService } from "@bitwarden/storage-core";
+import { UserId } from "@bitwarden/user-core";
+
+import { StateBase } from "./state-base";
+
+export class DefaultSingleUserState<T>
+  extends StateBase<T, UserKeyDefinition<T>>
+  implements SingleUserState<T>
+{
+  readonly combinedState$: Observable<CombinedState<T | null>>;
+
+  constructor(
+    readonly userId: UserId,
+    keyDefinition: UserKeyDefinition<T>,
+    chosenLocation: AbstractStorageService & ObservableStorageService,
+    private stateEventRegistrarService: StateEventRegistrarService,
+    logService: LogService,
+  ) {
+    super(keyDefinition.buildKey(userId), chosenLocation, keyDefinition, logService);
+    this.combinedState$ = combineLatest([of(userId), this.state$]);
+  }
+
+  protected override async doStorageSave(newState: T, oldState: T): Promise<void> {
+    await super.doStorageSave(newState, oldState);
+    if (newState != null && oldState == null) {
+      await this.stateEventRegistrarService.registerEvents(this.keyDefinition);
+    }
+  }
+}