[Backport 2021.1] Hdrp/backport test 2021 (#4402)

* [HDRP][DXR] Add coverage for lighting full screen debug mode in DXR Tests Projects (#4391)

* 5 new lighting debug mode scene

* RTAO + SSShadows

* build settings

* Light Cluster scene

* Contact shadows correct captures using BackBuffer

* ContactShadow scene

* forgot meta files

* Add coverage for path tracer alpha channel support (#4393)

* add-pt-alpha-automated-test

* Tidy up 5001 scene

* Disable DXR XR test (#4403)

* Add support for lighting full screen debug mode for HDRP tests #4367

* Fix automated tests

* upgrade path tracing alpha test

* 5001 updated unreadable image

* disable DXR XR 2005

Co-authored-by: Rémi Chapelain <[email protected]>
Co-authored-by: Remi Chapelain <[email protected]>

Author: sebastienlagarde