fix(kded): move to kdirwatch to reduce inotify footprint
Each QFileSystemWatch claims its own inotify instance. This is problematic because there is a default limit of 127 instances per user, fivolously claiming instances is therefore really poor behavior.
KDirWatch meanwhile shares the same underlying instance behind the scene so each thread would only have a single instance with N different watches on it.
Moving to KDW effectively reduces the inotify instance footprint of the kded module from N per Control to 0 since kded always has a kdirwatch for ksyscoca/kservice monitoring and our KDW is backed by the same instance.