Renaming native struct with redirect can break user defined structs

From https://udn.unrealengine.com/questions/444690/redirecting-ustruct-used-as-member-of-userdefineds.html

In 4.20 it was changed so soft object ptrs pointing to classes work correclty with +ClassRedirects lines in [CoreRedirects]. But, the same issue exists with Structs, which have a TSoftObjectPtr<UObject> that is actually always a struct. 

I may fix it to look for struct redirects at the same point it looks for class redirects, or I may fix it specifically in user defined struct loading. It's odd that it's stored as a <UObject> when it's actually a <UStruct>

1. Add a native struct to your project called OldNativeStruct
2. Create a User Defined Struct that uses that native struct, save it
3. In C++, rename the native struct to NewNativeStruct
4. Add a +StructRedirects=(OldName="/Script/GameName/OldNativeStruct",NewName="/Script/GameName/NewNativeStruct") to the [CoreRedirects] seciton in an engine ini
5. Reload editor and reopen user struct, it will have a broken reference