bug(mat-autocomplete): Autocomplete options are moving with dialog scrollbar

### Is this a regression?

- [ ] Yes, this behavior used to work in the previous version

### The previous version in which this bug was not present was

See: https://github.com/angular/components/issues/30254, it was present in 18 version.

### Description

Demo: https://github.com/lopatnov/autocomplete-issue

### Reproduction

StackBlitz link: I don't use StackBlitz, don't know how to upload demo here.
Steps to reproduce:
1. Open dialog with some elements, to have scroll in the dialog
2. Open Autocomplete items
3. Scroll down dialog scroll and you will see issue

### Expected Behavior

Options of Autocomplete should stay below autocomplete, as it was opened. They don't need to move with dialog scrollbar.

### Actual Behavior

When dialog scrollbar moves, then autocomplete options also moves.

### Environment

- Angular: 19.1.0
- CDK/Material: 19.1.1
- Browser(s): Chrome
- Operating System (e.g. Windows, macOS, Ubuntu): Windows

Inizia dalla riproduzione collegata all’indirizzo https://github.com/lopatnov/autocomplete-issue e riproduci il problema seguendo i passaggi indicati per il dialog, l’autocompletamento e la barra di scorrimento. Traccia quindi il comportamento del dialog e dell’autocompletamento di Angular Material coinvolto nel posizionamento, poi verifica che lo scorrimento del dialog lasci le opzioni sotto il trigger dell’autocompletamento.

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