[Console] Styling for split panel (#55530)

* Update z-index on output panel

* Add z-index setting to console input too

src/legacy/core_plugins/console/public/np_ready/application/styles/_app.scss

@@ -27,6 +27,9 @@
   // Required on IE11 to render ace editor correctly after first input.
   position: relative;
 
+  // Give the aria selection border priority when the divider is selected
+  z-index: 0;
+
   &__spinner {
     width: 100%;
   }
@@ -35,6 +38,8 @@
 .conApp__output {
   display: flex;
   flex: 1 1 1px;
+  // Give the aria selection border priority when the divider is selected
+  z-index: -1;
 }
 
 .conApp__textAreaLabelHack,