Implement cascade shadow mapping

[wpsimon09]

Currently shadowing is done with ray tracing however this approach appears to introduce more problems then solutions:

• bad performance for soft shadows
• noise that requires TAA to solve
• more complex code base with all AS updates
• inefficient volume rendering
• and more

I am gonna keep the ray traced shadows however main way of doing shadowing will be CSM.

This will solve most of the above problems:

• soft shadows will be achieved with percentage close filtering
• light shafts and other effects can be implemented efficiently using min/max skipping during ray marching
• easier code management

I will return to ray traced shadows once I will have some better rendering pipeline but for now I will do the shadows with CSM