fix: clear auth state immediately on removeUser

[SergioChan]

Closes/fixes #751

Summary

• dispatch USER_UNLOADED immediately after removeUser() resolves so auth context clears even when UserUnloaded events are not emitted by the runtime/mock environment
• keep existing onRemoveUser callback behavior unchanged
• add a regression test that starts from an authenticated state and verifies user + isAuthenticated are cleared right after removeUser()

Testing

• npm test -- AuthProvider.test.tsx

Checklist

• This PR makes changes to the public API
• I have included links for closing relevant issue numbers

[pamapa]

sound like a test issue you are trying to fix.
await userManager.removeUser(); calls at the end await this._events.unload();, which will trigger the USER_UNLOADED event in this library