[A11y] add aria label to change every instance on page (#188265)

## Summary

Closes https://github.com/elastic/search-team/issues/7675


### Checklist

- [x] Any text added follows [EUI's writing
guidelines](https://elastic.github.io/eui/#/guidelines/writing), uses
sentence case text and includes [i18n
support](https://github.com/elastic/kibana/blob/main/packages/kbn-i18n/README.md)

packages/kbn-search-api-panels/components/code_box.tsx

@@ -65,6 +65,13 @@ export const CodeBox: React.FC<CodeBoxProps> = ({
         <EuiContextMenuItem
           key={language.id}
           icon={`${assetBasePath}/${language.iconType}`}
+          aria-label={i18n.translate(
+            'searchApiPanels.welcomeBanner.codeBox.selectChangeAriaLabel',
+            {
+              defaultMessage: 'Change language to {languageName} for every instance on this page',
+              values: { languageName: language.name },
+            }
+          )}
           onClick={() => {
             if (setSelectedLanguage) {
               setSelectedLanguage(language);