VMware SVGA Graphics Driver Switches To NIR By Default

VMware's SVGA Gallium3D driver that provides OpenGL support within guest virtual machines running with VMware virtualization products is now finally defaulting to using the modern NIR intermediate representative rather than Gallium3D's TGSI.

While VMware acquired Tungsten Graphics years ago as the company behind Mesa, the SVGA Gallium3D driver they created has been one of the notable holdouts that has been slow to default to the modern NIR IR rather than TGSI. But Emma Anholt went ahead and finally changed the default in SVGA to using this IR that for years has been in use by the other prominent open-source Mesa drivers both for OpenGL and Vulkan.

SVGA has supported NIR but only when using the "SVGA_NIR=1" environment variable.

Functional changes from this MR should be the PBO GS path being taken once again (lost in the previous frontend NIR transition), and SVGA ingesting NIR instead of TGSI (it does its own nir_to_tgsi() call anyway). The benefit is fewer untested debug paths and less complexity in st_program.c

The change is part of next quarter's Mesa 23.2 release.