*Added FPrimitiveSceneDesc, a structure you can initialize with a description of the primitive you're trying to Add/Remove/Update in the FScene
-Added entry points in FSceneInterface to do those operations, legacy entry points using UPrimitiveComponent are untouched.
-The code that executes those operations in FScene has been refactored to be shared between the two entry points as much as possible to lessen the additional maintenance burden.
*Added FPrimitiveSceneProxyDesc/FStaticMeshSceneProxyDesc/FInstancedStaticMeshSceneProxyDesc, structures that hold all the necessary information to create a FPrimitiveSceneProxy/FStaticMeshSceneProxy/FInstancedStaticMeshSceneProxy without depending on AActors or UPrimitiveComponent.
-Those structures can be initialized by constructing them with the corresponding UPrimitiveComponents, or by constructing their default versions and initializing the desired fields.
-Creation code for FPrimitiveSceneProxy/FStaticMeshSceneProxy/FInstancedStaticMeshSceneProxy now takes all its info from those desc structures. They are created on demand during scene proxy creation for UPrimitiveComponents. This means no additional memory, and all serialized assets & blueprints are unaffected.
*Added IPrimitiveComponent/IStaticMeshComponent interfaces
-These allow for some editor-only interactions occurring during proxy creation, and serve as a common interface for some code that expected to manipulate UPrimitiveComponent/UStaticMeshComponents. For example FObjectCacheEventSink / FObjectCacheContext now uses those interfaces to associate the resources between various users and interactions like proxy recreation on shader/mesh changes occur through those interfaces.
* Misc
-Moved scene primitive related member variables into a new structure (FPrimitiveSceneInfoData) to facilitate code sharing and implementations of various related functionality (like SetLastRenderTime).
-Changed ObjectCacheContext to store associations between resources and components using component interfaces so that other systems creating proxies have the proper behaviors when resource changes require proxy recreation.
-Added natvis support so that component interfaces to UPrimitiveComponent/UStaticMeshComponent display the component ptr for easier debugging.
-Changed FMotionVectorSimulation to use UObject* instead of UPrimitiveComponent*, it was already using this internally
-Templatized some nanite helpers like ShouldCreateNaniteProxy & AuditMaterials since we need to use them from both UPrimitiveComponent & FPrimitiveSceneProxyDesc and it'll help make sure we keep them in sync.
#jira UE-191990
#rb Zach.Bethel, Ola.Olsson, Jason.Nadro, Krzysztof.Narkowicz
[CL 27200716 by dominic couture in ue5-main branch]
