Ps/improve state provider fakers (#7494)

* Expand state provider fakes

- default null initial value for fake states
- Easier mocking of key definitions through just the use of key names
  - allows for not exporting KeyDefinition as long as the key doesn't collide
- mock of fake state provider to verify `get` calls
- `nextMock` for use of the fn mock matchers on emissions of `state$`
- `FakeAccountService` which allows for easy initialization and working with account switching

* Small bug fix for cache key collision on key definitions unique by only storage location

* Fix initial value for test

libs/common/src/platform/state/key-definition.ts

@@ -151,8 +151,8 @@ export class KeyDefinition<T> {
       throw new Error("You must provide a userId when building a user scoped cache key.");
     }
     return userId === null
-      ? `${scope}_${userId}_${this.stateDefinition.name}_${this.key}`
-      : `${scope}_${this.stateDefinition.name}_${this.key}`;
+      ? `${this.stateDefinition.storageLocation}_${scope}_${userId}_${this.stateDefinition.name}_${this.key}`
+      : `${this.stateDefinition.storageLocation}_${scope}_${this.stateDefinition.name}_${this.key}`;
   }
 
   private get errorKeyName() {