bug(mat-sidenav): focus trapping is too aggressive under certain conditions

#### Reproduction

This issue seems to manifest under the following conditions:
- Sidenav is open in `over` or `push` mode (does not happen in `side` mode).
- Backdrop is disabled (this is necessary to be able to click in the content area of a `over` or `push` sidenav.
- App is using the `ConfigurableFocusTrap` (does not happen with the deprecated `FocusTrap`).

Steps to reproduce:
https://stackblitz.com/edit/angular-avy29p?file=src%2Fmain.ts
1. click to focus the "Content" input

#### Expected Behavior

"Content" input remains focused.

#### Actual Behavior

"Drawer" input immediately steals focus.

Comienza con la reproducción vinculada de StackBlitz en src/main.ts y verifica el comportamiento con un over o push sidenav, backdrop deshabilitado y ConfigurableFocusTrap. Traza el comportamiento del foco cuando se hace clic en el Content input; se considera terminado cuando el Content input permanece enfocado en lugar de que el Drawer input reciba el foco.

Escrito por el modelo de indexación a partir del texto del issue.