searchenginetracker: Optimize direct/recursive folder lookups

searchenginetracker: Optimize direct/recursive folder lookups

tracker:uri-is-descendant/parent has the unfortunate side effect of
rendering the collation mechanisms in the database useless, so those
require full table scans to be validated.

Performing these as pure string comparisons will perform much better,
as those allow the underlying sqlite to rely on its own collation
to perform the search, which can be significantly faster with many
elements in the database.

https://bugzilla.gnome.org/show_bug.cgi?id=758407