microsoft/compiler: Error propagation for unsupported instruction types

This change adds error handling to nir_to_dxil for when the compiler sees an instruction it does not know how to handle. Exposing these internal compiler errors can be extremely useful for debugging compiler failures found when e.g. integrating Mesa into a larger project.

This adds a struct dxil_logger, similar to struct clc_logger. It replaces calls to NIR_INSTR_UNSUPPORTED to log to this new logger, rather than crashassert`.

Note: this is a breaking change for existing users of nir_to_dxil and spirv_to_dxil.