[Unified Search][Lens] Focus selectable search inputs in dropdowns (e…

…lastic#191213)

## Summary

Adds `autoFocus` search input in dropdown for the global **Data view**
selector and the **Lens chart switch**. Now clicking on either dropdown,
the focus will automatically be on the input for the user to start
typing to filter selectable items. This does not change the tab indexing
of the surrounding elements.

### Data view picker

![Zight Recording 2024-08-23 at 09 11 47
AM](https://github.com/user-attachments/assets/c5cf9981-4e79-4216-b1ae-0ef5da8fe62a)

### Lens chart switch

![Zight Recording 2024-08-23 at 09 14 09
AM](https://github.com/user-attachments/assets/7fb117b5-0bb7-4204-a606-264ce12a1f6d)

closes elastic#189686

### Checklist

- [ ] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios
- [x] Any UI touched in this PR is usable by keyboard only (learn more
about [keyboard accessibility](https://webaim.org/techniques/keyboard/))
- [x] Any UI touched in this PR does not create any new axe failures
(run axe in browser:
[FF](https://addons.mozilla.org/en-US/firefox/addon/axe-devtools/),
[Chrome](https://chrome.google.com/webstore/detail/axe-web-accessibility-tes/lhdoppojpmngadmnindnejefpokejbdd?hl=en-US))
- [x] This was checked for [cross-browser
compatibility](https://www.elastic.co/support/matrix#matrix_browsers)

---------

Co-authored-by: Elastic Machine <elasticmachine@users.noreply.github.com>
Co-authored-by: Marta Bondyra <4283304+mbondyra@users.noreply.github.com>

src/plugins/unified_search/public/dataview_picker/dataview_list.tsx

@@ -149,6 +149,7 @@ export function DataViewsList({
       searchProps={{
         id: searchListInputId,
         compressed: true,
+        autoFocus: true,
         placeholder: strings.editorAndPopover.search.getSearchPlaceholder(),
         'data-test-subj': 'indexPattern-switcher--input',
         ...(selectableProps ? selectableProps.searchProps : undefined),