[BUG] TapToPlace doesn't start placement when StartPlacement() is called just after prefab creation #784

/// <summary>
/// Verify TapToPlace can start placement when method is called before its own Start.
/// </summary>
[UnityTest]
public IEnumerator TapToPlaceIsBeingPlacedBeforeStart()
{
    // Disable gaze interactions for this unit test;
    InputTestUtilities.DisableGazeInteractor();

    // Set up GameObject with a SolverHandler
    var testObject = GameObject.CreatePrimitive(PrimitiveType.Cube);
    var solverHandler = testObject.AddComponent<SolverHandler>();
    var solver = testObject.AddComponent<TapToPlace>();

    // Disable smoothing so moving happens instantly. This makes testing positions easier.
    solver.Smoothing = false;

    // Set it to track interactors
    solverHandler.TrackedHandedness = Handedness.Both;
    solverHandler.TrackedTargetType = TrackedObjectType.Interactor;
    var lookup = FindObjectUtility.FindAnyObjectByType<ControllerLookup>();
    var leftInteractor = lookup.LeftHandController.GetComponentInChildren<MRTKRayInteractor>();
    var rightInteractor = lookup.RightHandController.GetComponentInChildren<MRTKRayInteractor>();
    solverHandler.LeftInteractor = leftInteractor;
    solverHandler.RightInteractor = rightInteractor;

    int onPlacingStartedCount = 0;
    int onPlacingStoppedCount = 0;
    solver.OnPlacingStarted.AddListener(() => onPlacingStartedCount++);
    solver.OnPlacingStopped.AddListener(() => onPlacingStoppedCount++);

    // Call immediately whithout the TapToPlace Start being called
    solver.StartPlacement();

    yield return RuntimeTestUtilities.WaitForUpdates(1);

    Assert.IsTrue(solver.IsBeingPlaced, "TapToPlace should have started.");
    Assert.AreEqual(1, onPlacingStartedCount, "TapToPlace should have invoked event OnPlacingStarted exactly 1 time.");
    Assert.AreEqual(0, onPlacingStoppedCount, "TapToPlace shouldn't have invoked event OnPlacingStarted.");
}