[WIP] Merge the PodioDataSvc into k4DataSvc

[tmadlener]

BEGINRELEASENOTES

• Merge the internal PodioDataSvc into the visible k4DataSvc and make that part of the core library instead of the plugins. Fixes Merge k4DataSvc and PodioDataSvc #104
• Remove the FCCDataSvc.

ENDRELEASENOTES

• Check if stack still builds (yes)
• Wait for feedback on removal of FCCDataSvc
• Builds on PodioInput: Read all collections by default, allow to limit them with the collections property #162
• Builds on Make "always read EventHeader" collection more robust #161

[tmadlener]

Brought this back to live via some cherry-picking and some merge resolutions. Things are not yet completely working yet, but it should be easier to fix the remaining issues now. One of the open things is the following warning:

https://github.com/key4hep/k4FWCore/actions/runs/9210346272/job/25337137482?pr=163#step:3:275