Memory Leak in Injector

I've encountered a possible memory leak while using `OverlayRef` and `Injector`.

#### Reproduction

Inside `AppComponent` there is a click event on a button. That click event will generate an array and pass that array to another component using `ComponentPortal`

The constructor and the click event from `AppComponent`:

```
// ? AppComponent constructor
constructor(private overlay: Overlay) {
this.#overlayRef = this.overlay.create({
positionStrategy: this.overlay
.position()
.global()
.centerHorizontally()
.centerVertically(),
hasBackdrop: true,
});

this.#overlayRef.backdropClick().subscribe(() => this.#overlayRef.detach());
}

onClick(){
const output = new Array(1000).fill('asfasdf');
this.#overlayRef.attach(
new ComponentPortal(
MyComponent,
null,
Injector.create({
providers: [{ provide: MY_TOKEN, useValue: output }],
})
)
);
}
```

#### Actual Behavior

It looks like each time the modal is created the data generated and injected in the component, but once the modal disappears, the data is not removed from the memory.


#### Environment

- Angular:
- "@angular/core": "~11.2.5",

- CDK/Material:
- "@angular/cdk": "^11.2.4",
- Browser(s): Chrome
- Operating System (e.g. Windows, macOS, Ubuntu): Windows10

Il report nomina AppComponent, MyComponent, OverlayRef, Injector e ComponentPortal; inizia riproducendo clic ripetuti e controllando gli heap snapshot. Traccia il ciclo di vita attach/detach dell'overlay e i riferimenti di Injector.create, quindi verifica se l'array iniettato viene rilasciato dopo la chiusura e acquisisci il risultato in un test di regressione o in una diagnosi documentata.

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