Upgrade Chat Search

[gnunicorn]

The search for chat is outdated in our current model. Rather than having a sticky search (keeping the value of the text field) we should consider aligning the search with the way it works in the rest of the system:

1. filtering by type should stick as is
2. clicking the search text box should open another dialog with the search text field autoselected so the user can start typing
3. upon selection of a chat, we navigate there without keeping the search-screen in the navigation history

Additionally, global search should include chats as well (under spaces) and navigate the same way.