Add new Detector flags for ITk

Adding dedicated detector flags for Upgrade detectors, to allow configurations more independently.

A few questions:

• Presumably we should forbid the ITk and ID to be on at the same time - is there are preferred way to do this? (see below - this will come later)

• At the moment, SimulateHGTD will set SimulateID to true. Presumably this should rather be SimulateITk in future, and is there a reason we only do this for the Simulate flags, not the Geometry ones? (HGTD now moved to SimulateITk)

cc @jchapman @asalzbur @goetz @sroe @cohm