Support building `master` with Geant4 10.6
From version 10.6, Geant4 no longer exports G4MULTITHREADED in the compiler flags as -DG4MULTITHREADED. This symbol must be the same between a build of Geant4 and any client application, so is instead exported into a configuration header included in the common G4Types.hh header.
Update components of Athena that rely on this symbol so that they explicitly #include G4Types.hh before using it.
InnerDetector has a private dependency on Geant4 headers added so that it picks up the needed header path.
This prepares Athena for tests/builds with the new version without affecting use of older versions of Geant4, as the inclusion of G4Types.hh does not affect the public or private API/ABI or add additional public dependencies.
Needed to support ATLASSIM-4217