Removed direct access to currently compiling BP class to restrict unguarded mutation.
Const-corrected various accessors and overrides.
Moved UObject-based compiler subsystems to 'handlers' and removed UObject dependency.
Moved from set of virtual functions on subsystems/handlers to a restricted set of contexts passed to specific multicast delegates that handlers subscribe to.
Removed anim class subsystems.
Moved property access code to engine module (editor code is still in a plugin).
Fixed nativized builds where anim BPs have nativized/non-nativized classes in the hierarchy
#rb Dan.OConnor
#jira none
[CL 14278258 by Thomas Sarkanen in ue5-main branch]
