Publish auxiliary data

This MR introduces a new mechanism to publish/store auxiliary data, on request, to the output SQLite file.

The auxiliary data can be published both from GeoModel plugins, by using the interface provided by the updated GeoModelKernel/GeoPublisher, and from plain GeoModel code, through direct access to methods exposed by GeoModelIO/GeoModelWrite.

Also, the auxiliary data can be defined inside the C++ code on-the-fly, or read from local XML data files. In the latter case, GeoModelATLAS/GeoModelDataManagers is used and so a dependency to that is introduced.

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This has a sibling MR in GeoModelATLAS: https://gitlab.cern.ch/atlas/geomodelatlas/GeoModelATLAS/-/merge_requests/3

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The changes introduced by this MR have been presented in more details at the latest ATLAS Software& Computing Week: https://indico.cern.ch/event/969847/contributions/4201226/