Cdk Overlay backdrop does not respect noopanimations

[phyrephox]

Reproduction

Use StackBlitz to reproduce your issue: https://stackblitz.com/fork/components-issue

Steps to reproduce:

1. import NoopAnimationsModule
2. Create a dialog
   https://stackblitz.com/edit/angular-fdgmah (based on example dialog stackblitz)

Expected Behavior

What behavior were you expecting to see?

The dark overlay appears immediately with no animation

Actual Behavior

What behavior did you actually see?

The overlay backdrop fades in over 400ms.

Environment

• Angular: 9.1
• CDK/Material: 9.1
• Browser(s): Chrome
• Operating System (e.g. Windows, macOS, Ubuntu): Linux

[hsuanxyz]

Looks related to #10145