turnip: Add a TU_DEBUG=perf debug option.

For doing performance investigation, I often find it useful to have a "are
we tripping over any of our performance TODOs?" flag, so add it and use it
in a few of the TODOs.

This also greatly cleans up the deqp-vk logs.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/16316>
6 files changed