Introduce a SearchBar

[leolost2605]

Fixes #794

Introduce a search bar widget since we are probably gonna need search in more places if we're going to implement the library.

[Oowoosh0]

Overall it looks good to me. Just a couple of smaller issues I found:

• When nothing matches the search term then the "Queue is Empty" Placeholder gets shown. Probably it would be better to display a placeholder here that reflects that the search didn't return any results.
• There are some performance issues if the queue is larger (couple hundred songs). The UI freezes for a bit on every character entered into the search bar. I guess it is unavoidable that filtering a longer list takes a bit, but ideally the UI should stay responsive.
• If I clear the queue while a search is applied and then add new songs that search is automatically applied again. Maybe it's better to reset the search filter when clearing the queue. But I'm not really sure which of the two would be the expected behaviour for most people.

[danirabbit]

@Oowoosh0 Pushed a couple commits to address review comments. I think performance should be better here since we've switched to ListView previously

[ryonakano]

Hmm I think it would be more natural if the placeholder text changes according with typing in search entry 🤔

[danirabbit]

@ryonakano fixed!