perf(cdkTextareaAutosize): Skip height measurements when textarea value is empty

### 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

_No response_

### Description

Calls to _measureScrollHeight, which trigger css layout, are not needed when there's nothing in the text field. In this case, simply set the height to 1 row (height of one line).

See internal CL 421826236 for more context.

### Reproduction

Steps to reproduce:
1. Bootstrap a textarea with cdkTextareaAutosize that has value of '' (empty)

### Expected Behavior

_measureScrollHeight() called only when there's a non-empty value.

### Actual Behavior

_measureScrollHeight() is called regardless of value.

### Environment

- Angular: 13
- CDK/Material: 13
- Browser(s): All
- Operating System (e.g. Windows, macOS, Ubuntu): All

Commencez par l’implémentation de cdkTextareaAutosize et suivez le point d’entrée _measureScrollHeight en utilisant un textarea dont la valeur est vide. Vérifiez que les valeurs vides utilisent une hauteur d’une ligne sans mesure, tandis que les valeurs non vides conservent le comportement de mesure ; ajoutez ou mettez à jour le test pertinent si l’emplacement du test de l’implémentation est identifié.

Rédigé par le modèle d'indexation à partir du texte de l'issue.