Legacy workarounds for Visual Studio non thread-safe initialization
of function local objects with static storage duration are removed:
* Remove LeakChecked
* Remove StaticObject
* Remove SharedSingleton
An alternative to the unity build, the classic build compiles each
translation unit individually. This adds more modules to the classic build:
* Remove unity header app.h
* Add missing includes as needed
* Remove obsolete NodeStore backend code
* Add app/, core/, crypto/, json/, net/, overlay/, peerfinder/ to classic build