intel/ir: Use brw::performance object instead of CFG cycle counts for codegen stats.

intel/ir: Use brw::performance object instead of CFG cycle counts for codegen stats.

These should be more accurate than the current cycle counts, since
among other things they consider the effect of post-scheduling passes
like the software scoreboard on TGL.  In addition it will enable us to
clean up some of the now redundant cycle-count estimation
functionality in the instruction scheduler.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>