Add default tag for ITk if TrkDetFlags are not properly configured
Following the sweep of !33017 (merged) to 21.9, MuonRec is now included in the configuration of Digitization (which should not normally be the case). This caused issue for ITk+NSW, since MuonRec tries to load the Tracking Geometry material map, but the necessary TrkDetFlags are not configured during Digitization (since they are for reconstruction).
While a solution to avoid MuonRec being included in digi is sought, an interim solution is to have an existing Tracking Geometry tag set by default for ITk, such that no ERROR is triggered due to a failed retrieval. NB This map is not actually used anywhere in digitization, so the actual tag loaded should not matter.