anv: shader printf debugging
What does this MR do and why?
While debugging some new raytracing tests (!25146 (merged)), I had to come up with a way to print out values in the lowering code.
The MR is a bit of a cleaned version of what I came up with initially.
It's also here to replace a tool that @mslusarz wrote a few months ago and that is mesh specific (!21839 (closed)).