* ATOM-15369 Expose sorting paramers to DynamicDrawContext's draw functions
LYN-3352 LyShine: First element in Hierarchy does not properly draw in UI Editor
Add function to DynamicDrawContext to support set sort key for followed draw calls.
Use different sort key for background draw and top layer draw in UI canvas.
* Move Draw2d.h to Include folder
* Initial phase of UI Canvas Editor rendering with Atom
* Simplify Draw2d by removing BeginDraw2d/EndDraw2d which is no longer needed
* Fix compile errors for non-unity builds
Steve Pham
michabr
abrmich
Vicky
alexpete