[new-webui] Focus/refocus query input box for ease of use

[kirkrodrigues]

Request

• When a user clicks on the search page, we should set the focus to the query input box so that the user doesn't need to do so manually before they can search.
• If a user was focused on the query input box and then they press enter to search, after the search completes, focus should return to the query input box.

Technically, we could always set the focus to the query input box after a query completes, but this might affect usability. Ideally, focus should return to whatever input the user used before starting the query (moreover, we should support starting a new query while the previous query is running without having to manually cancel the query, but that's a different issue). So if the user was focused on the time range selector before starting a query, focus should return to it after the query completes.

Possible implementation

Not entirely sure.

[kirkrodrigues]

Not entirely complete.