feat(segmented-control-item): enhance component's interactivity states (#11477)

**Related Issue:**
[#10013](#10013)

## Summary

Update focus ring `z-index` to sit on top of border container.

Author: aPreciado88

packages/calcite-components/src/components/segmented-control-item/segmented-control-item.scss

@@ -45,6 +45,7 @@
 :host(:focus) {
   @apply focus-inset;
   outline-offset: -1px;
+  z-index: 1;
 }
 
 .label--scale-s {