Various terrain improvements: (#3942)

* Various terrain improvements:
- Height now stored in a R16_unorm to decrease the amount of memory / memory bandwidth needed for the height field
- Many simplifications to the feature processor
- Added a shader to render to the depth pre pass
- Pulled common functionality needed by depth and forward to a common include shader
- Forward shader now outputs to all the expected render targets
- Adjusted the way normals and lighting are being calculated

Signed-off-by: Ken Pruiksma <pruiksma@amazon.com>

* Adding missing shader files. Updated terrain shader to alter the color slightly with height.

Signed-off-by: Ken Pruiksma <pruiksma@amazon.com>

* Removed pixel shader code from terrain depth pass

Signed-off-by: Ken Pruiksma <pruiksma@amazon.com>

* Renamed the depth pass shaders to no longer indicate they include a pixel shader.

Signed-off-by: Ken Pruiksma <pruiksma@amazon.com>

* Removing unneeded code from TerrainCommon.azsli

Signed-off-by: Ken Pruiksma <pruiksma@amazon.com>

Code/Editor/Objects/BaseObject.h

@@ -798,8 +798,6 @@ private:
     //////////////////////////////////////////////////////////////////////////
     //! Area radius around object, where terrain is flatten and static objects removed.
     float m_flattenArea;
-    //! Every object keeps for itself height above terrain.
-    float m_height;
     //! Object's name.
     QString m_name;
     //! Class description for this object.