bug(mat-button, mat-icon): mat-icon inside of mat-button are truncated

### Is this a regression?

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

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

Not sure which

### Description

Using Angular 19 with angular material, if I put a `mat-icon` element inside of a `mat-button`, the icon is not completely visible. It is truncated a little at its top and bottom. See reproduction StackBlitz below.

### Reproduction

Forked the "Button Angular Component" example to display the problem.

Editor: https://stackblitz.com/edit/3zsvfedr?file=src%2Fexample%2Fbutton-overview-example.html
Application: https://3zsvfedr.stackblitz.io

See the second button in the "Basic" "Raised" "Stroke" and "Flat" table rows.

### Expected Behavior

I would expect the icon to be fully visible, not truncated. In case of the `add_circle` icon, I would expect its shape to be perfectly round.

### Actual Behavior

The top and bottom of the icon are truncated (cropped) which makes it painfully _not round_.


### Environment

- Angular: 19
- CDK/Material: 19.2.7
- Browser(s): Edge, Chrome and Firefox
- Operating System: Windows

Start with the linked StackBlitz reproduction and compare the second buttons in the Basic, Raised, Stroke, and Flat examples. Trace the Angular Material mat-button and mat-icon rendering and styling involved in the clipping. Done means the icon is fully visible and the add_circle icon appears round across the reported browsers.

Written by the indexing model from the issue text.