feat(dialog): Support async `MatDialogConfig.closePredicate`

### Feature Description

For a long time we wanted to be able to cancel dialog closure, in #14292. It was solved via a new option, `closePredicate`, in #14292. But that new option does not support async code. And so we cannot, for example, ask user for the confirmation to close the dialog (via a second dialog), nor do XHR to verify things on server-side.

This kind of use case was already mentioned by @teolag in https://github.com/angular/components/issues/14292#issuecomment-2828734239, but that specific part of the message was left unanswered. And @Nakira had to come up with a custom solution to solve this in https://github.com/angular/components/issues/14292#issuecomment-2907749489

### Use Case

I want the dialog closure to wait until I know whether it can be closed. Possibly via asking the user that he is OK to lose all the data he just input in the dialog, like so:

```ts
this.matDialog.open(MyDialogComponent, {
closePredicate: async () => await askUserIfReallySure(),
});
```

Start with the existing MatDialogConfig.closePredicate behavior and the dialog closure flow; the issue gives the public option and an async usage example. Trace how the predicate result is handled, then verify that dialog closure waits for asynchronous confirmation and still supports cancellation.

Written by the indexing model from the issue text.