Added wave wide work distribution of coverage testing through bitmask tiles. This didn't prove to be faster in my test but I'm checking it in for posterity and the work distribution code is good and may be useful elsewhere. We can delete the tile distribution from the rasterizer later.
#rb rune.stubbe
#ROBOMERGE-AUTHOR: brian.karis
#ROBOMERGE-SOURCE: CL 18415357 in //UE5/Release-5.0/... via CL 18415390
#ROBOMERGE-BOT: STARSHIP (Release-Engine-Staging -> Release-Engine-Test) (v897-18405271)
[CL 18415405 by brian karis in ue5-release-engine-test branch]