Fix Scintillator and Mylar for Tile TestBeam configurations (ATLASSIM-4733)

After the changes in !35795 (merged) the test_TestBeamSim.sh script stopped working - see ATLASSIM-4733. This commit adds back the removed materials, but fixes their definitions according to Sven's recommendations from ATLASSIM-4679. Prior to !35795 (merged), there were two G4Material objects called "Scintillator". One defined in MaterialDescriptionTool and one from the Tile geometry. Afterwards there was one G4Material objected called "tile::Scintillator". The version defined by MaterialDescriptionTool was used in the Tile Test Beam. It is an open question whether the actual intention of whether "tile::Scintillator" should have actually been used.