fix(material/core): icons not aligned inside mat-option

Fixes that icons projected inside an MDC-based `mat-option` weren't centered and didn't have the correct margin like the non-MDC version.

Fixes #26024.

Author: crisbeto

src/material/core/option/option.html

@@ -1,6 +1,8 @@
 <mat-pseudo-checkbox *ngIf="multiple" class="mat-mdc-option-pseudo-checkbox"
     [state]="selected ? 'checked' : 'unchecked'" [disabled]="disabled"></mat-pseudo-checkbox>
 
+<ng-content select="mat-icon"></ng-content>
+
 <span class="mdc-list-item__primary-text"><ng-content></ng-content></span>
 
 <!-- See a11y notes inside optgroup.ts for context behind this element. -->

src/material/core/option/option.scss

@@ -46,8 +46,10 @@
     }
   }
 
+  .mat-icon,
   .mat-pseudo-checkbox {
     margin-right: mdc-list-variables.$side-padding;
+    flex-shrink: 0;
 
     [dir='rtl'] & {
       margin-right: 0;