In DICOM plugin, remove link-time dependency to auto-load DicomRTIO module

Summary:

• Add check against auto-load dependencies that was introduced for modules in T26980 resp. D224 also to plugins

• Remove auto-load dependency to DicomRTIO

• Use FileReaderRegistry to indirectly access DicomRTIO services in DICOM plugin

Test Plan: I manually loaded our RTStruct, RTDose, and RTPlan test datasets through the DICOM plugin.

Reviewers: floca, O1 MITK Reviewer Group I, O3 MITK Reviewer Group II

Reviewed By: floca, O1 MITK Reviewer Group I, O3 MITK Reviewer Group II

Tags: MITK

Maniphest Tasks: T27243

Differential Revision: https://phabricator.mitk.org/D266