search: Make search stack/notepad entries selectable
Created by: fkling
This commit adds the ability to select search stack/notepad entries via click, ctrl/meta+click and shift+click. The entries can also be selected via space, ctrl+space and shift+space if they are focused.
In the end I went with role=listbox and role=option for the entries, because I think that comes closes to how we want this component to behave eventually. But note that more work is required to make this component fully usable via the keyboard.
I also switched to using <section>
since that seemed appropriate according to this guide.
https://user-images.githubusercontent.com/179026/155176072-60757880-11c2-42c9-a1a5-e6a933fabbc3.mp4
Test plan
New unit tests for selecting with and without modifier keys and via keyboard.