Add optional support for TrackingGeometry conditions data in ExtrapolationEngine
requested to merge goetz/athena:ExtrapolationEngine_master_support_for_TrackingGeometry_cond_data into master
By default the TrackingGeometry will still be provided by the TrackingGeometrySvc, but with this patch the TrackingGeometry can alternatively be obtained from the conditions store. Once all clients are migrated the default will be changed, it will be obtained from the conditions store, and the support of the TrackingGeometrySvc will be retired.
This addresses ATLASRECTS-5907.