Flip datasets and workspaces in the search page sidebar

[hoyla]

Practically no one is searching datasets, so we should put workspaces at top so people know they exist in the search page.

(I also think we should display single workspaces as chips in the search field, like we do for workspace folders, so people can see what they're searching. If a user searches multiple workspaces the chip could just say "multiple workspaces". But that should be a separate card)