AMD RDNA4 Paired Context Reg Feature Merged For RADV To Potentially Help Performance

After various commits to Mesa 25.1 in recent days in preparing for a new paired context registers feature of AMD RDNA4 (GFX12 graphics), the feature today is wired up for the Radeon Vulkan driver "RADV" with the upcoming Mesa 25.1 release. This feature has the possibility of helping performance for new AMD RDNA4 hardware but the performance benefits at this time aren't clear...