SearchListItem: use Granite.ListItem and HeaderLabel

[danirabbit]

• Granite.HeaderLabel handles laying out secondary text for us here and we get a11y free. The only thing we lose is multiple lines of description text
• Use Granite.ListItem here as well for free padding and Granite.Box for spacing
• Instead of relying on max-width-chars we can use Adw.ClampScrollable

BEFORE

AFTER