bug(FocusMonitor): If a focused element becomes [disabled], attached FocusMonitor still reports the element as focused (FF, non-Chromium Edge).

#### Reproduction

Stackblitz: https://stackblitz.com/edit/angular-atdzsd

*Steps to reproduce:*

1. Open the Stackblitz above on either FF or non-Chromium Edge. The Stackblitz contains a `mat-checkbox` that disables itself when activated.
2. Activate the `mat-checkbox` with space. Observe that the `mat-checkbox` is now indeed disabled.

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#### Expected Behavior

I'd expect that the `mat-checkbox` loses its focus styles (and essentially all of the issues in "Actual Behavior" don't occur).

#### Actual Behavior

Observe the following after activating the `mat-checkbox` with space:

1. The `mat-checkbox` still has the classes `.cdk-focused` and `.cdk-keyboard-focused`.
2. As a result, the `mat-checkbox` still has focus styles.
3. If you query for the `document.activeElement`, it returns the `mat-checkbox`.
4. Subsequent mouse clicks & focus events on the page do not cause the `mat-checkbox` to lose its focus styles (i.e. it looks focused essentially forever).

All of the above are unexpected.

#### What's Happening

On FF and non-Chromium Edge, when a focused element is `[disabled]` it (1) remains the `document.activeElement` and (2) consequently no `blur` event is emitted. These appear to be browser bugs. As a result of this behavior, the attached `FocusMonitor` on `mat-checkbox` (and other components like `mat-button`) never receives a `blur` event to remove the `.cdk-focused` and `.cdk-keyboard-focused` classes on the element.

#### Potential Solution

We could add some work-around logic to `FocusMonitor` to listen if a monitored element becomes `[disabled]`, and if so, do the same thing we'd do if the element was actually blurred.

#### Environment

- Angular: Latest
- CDK/Material: Latest
- Browser(s): FF, non-Chromium Edge
- Operating System (e.g. Windows, macOS, Ubuntu): macOS

Bắt đầu bằng cách tái hiện vấn đề trong Stackblitz được liên kết với FocusMonitor và mat-checkbox trên Firefox hoặc Edge không dựa trên Chromium. Theo dõi cách FocusMonitor xử lý một phần tử đang được focus trở thành bị vô hiệu hóa; hoàn tất khi checkbox bị vô hiệu hóa mất các class focus và các sự kiện chuột hoặc focus về sau không còn khiến nó giữ kiểu hiển thị như đang được focus.

Do mô hình lập chỉ mục viết ra từ nội dung của issue.