DataModelRunTests+DataModelTestDataRead+DataModelTestDataCommon: Test propagating decoration dependencies though ShallowCopy.

Add tests for using ShallowCopyDecorDeps to propagate decoration dependencies through ShallowCopy.

Do a bit of refactoring in the process: split up DataModelTestDataRead/xAODTestShallowCopy to DataModelTestDataCommon/xAODTestShallowCopy (handling only the types defined in Common) and DataModelTestDataRead/xAODTestShallowCopyHVec. Also move them to use handles, etc.

Because this moves a component between packages, there may be duplicate component warnings until there's a full rebuild.