fix(select): chevron icon is now an ionicon (#26484)

BREAKING CHANGE:

The `icon` CSS Shadow Part for `ion-select` now targets an `ion-icon` component.

core/src/components/select/select.scss

@@ -65,7 +65,11 @@ button {
 }
 
 .select-icon {
+  @include margin(0, 0, 0, 4px);
+
   position: relative;
+
+  width: 13px;
 }
 
 .select-text {
@@ -81,21 +85,3 @@ button {
 
   overflow: hidden;
 }
-
-.select-icon-inner {
-  @include position(50%, null, null, 5px);
-  @include margin(-2px, null, null, null);
-
-  position: absolute;
-
-  width: 0;
-  height: 0;
-
-  border-top: 5px solid;
-  border-right: 5px solid transparent;
-  border-left: 5px solid transparent;
-
-  color: currentColor;
-
-  pointer-events: none;
-}