feat(Material Select) - Way to set first option active manually

#### Way to set first option as active manually in Material Select

The feature to let first option active in the options displayed using material select.
i.e. One should be able to manually/programmatically set the first option in the dropdown as active.

#### Use Case

While implementing search filter using Material Select component ( i.e. using an Input element within mat-select ) the active item toggles based on the default behaviour of keyboard interaction i.e. it sets the item active as per the matching character user has pressed on keyboard. This causes inconsistency while implementing custom filtering and may lead disturbance in the focus as per UX perspective.

The feature for manually setting the first option active can help resolve the above scenario.

Tried using `this.matSelect._keyManager.setFirstItemActive();` (matSelect is of type Material Select) but the default search behaviour causes inconsistency and sometimes option other than the first option gets active

**Sample demo for Drop Down Search using Material Select :**
https://stackblitz.com/edit/angular-ivy-q1bvhb

Comienza con la reproducción vinculada de StackBlitz e inspecciona la interacción del teclado de Material Select y el comportamiento de la opción activa. Determina cómo un consumer podría activar manualmente la primera opción filtrada sin que el comportamiento de búsqueda predeterminado la sobrescriba. Se considera terminado cuando el comportamiento solicitado se expone de forma coherente y está cubierto para el caso de uso de filtrado personalizado.

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