cdkDragStartDelay behavior has changed in version 8.1.0

It seems that the behavior of drag start delay has been changed between Angular CDK versions 8.0.0 and 8.1.0. I think this is a breaking change since it completely changes the way users interact with draggable items. I am not sure if the current behavior is really intended.

#### Reproduction

8.0.0: https://stackblitz.com/edit/angular-cdkdragstartdelay-80
8.1.0: https://stackblitz.com/edit/angular-cdkdragstartdelay-81

Steps to reproduce:
1. Click on any item.
2. Try to drag it as soon as possible.


#### Expected Behavior

In the previous version it did not matter if the mouse was clicked or immediately moved. The dragging started anyway after the specified delay.

#### Actual Behavior

In the current version the item is not being dragged when you move the mouse immediately after the initial click. It only works if you stay at the click position for the specified delay time and then move the mouse.

#### Environment

- Angular: 8.0.0+
- CDK/Material: 8.1.0+
- Browser(s): Google Chrome
- Operating System (e.g. Windows, macOS, Ubuntu): Fedora Linux 29

Inizia confrontando le due riproduzioni StackBlitz collegate per Angular CDK 8.0.0 e 8.1.0, concentrandoti su cdkDragStartDelay e sulla sequenza di fare clic e spostare immediatamente. Traccia l’implementazione del trascinamento della selezione utilizzata dalle riproduzioni e verifica il comportamento rispetto ai risultati attesi ed effettivi indicati.

Scritto dal modello di indicizzazione a partire dal testo della issue.