radv,aco: fix certain derivatives in divergent control flow

This fixes games calculating derivatives of inputs and constants in divergent control flow by moving the nir_op_fdd(x|y)_* and coordinate interpolations/constant copies outside control flow (and into a linear vgpr, in the texture sampling case).

To implement cube map and 1D/GFX9 cases, it also adds a pass to lower coordinates for these operations in NIR.

This case is required to work by the Direct3D 11 specification and is often done, sometimes even by native Vulkan applications.