UI: Use HDS::Toast for flash messages (#25459)

* Move global-flash to HDS-specified area

* Add flash-toast component

* use flash toast for flash messages

* Use spacing vars

* Remove unnecessary key

* Cleanup + tests

* Remove nondeterministic build warning

* add changelog

* I wish this was automatic

ui/lib/open-api-explorer/addon/routes/index.js

@@ -17,7 +17,6 @@ IF YOUR TOKEN HAS THE PROPER CAPABILITIES, THIS WILL CREATE AND DELETE ITEMS ON
 Your token will also be shown on the screen in the example curl command output.`;
     this.flashMessages.warning(warning, {
       sticky: true,
-      preformatted: true,
     });
   }
 }