KF6 Dolphin depends on kio-extras, for kcm_trash embedded in settings

A better version of sysadmin/repo-metadata!170 (merged), to last beyond the next regeneration of dependency data. Same idea as before, just listed at the source now.

Question for maintainers: Should the ifdef in dolphinsettingsdialog.cpp also include macOS? I figure Dolphin won't be able to change/include the macOS trash settings? So I put the dependency into the "Linux/FreeBSD only" section for now, as opposed to creating a new one that excludes Windows but includes macOS.

CC @nicolasfella, please have a look if this now works with your dependency script. I managed to get it barely running (had to fiddle with directory structures to make it work on my nested kdesrc-build checkout) and it appears to show up in the right spot. But I don't have all of your other setup for generating the full list.