Added ITkCaloExtension config
This MR adds a new ITk-specific configuration for the CaloExtensionBuilder. With respect to the Run-3 configuration, it uses the new ITkExtrapolatorCfg instead of the AtlasExtrapolatorCfg. It also feeds dummy DetEleCollKey introduced due to https://its.cern.ch/jira/browse/ATLASRECTS-4688 for compatibility with TP converters but likely not relevant for Run-4 configuration.