High level realization methods were removed from Component. It was agreed that only the top-level (aggregator) should have that ability to realize the system and only to provide access for scripting users.
The C++ API is complete since any Component including model provides getSystem() and realize(State, Stage) can be called directly on the system.

Added realize<Stage> methods to Model to provide access via scripting where the MultibodySystem and Stage are not wrapped.

These need to be tested via scripting.

An assortment of fixes to find and replace bugs that renamed realize<...> to extendRealize<...> in comments that were refering to the System methods and not virtual methods on Component.