intel: INTEL_MEASURE cpu mode

intel: INTEL_MEASURE cpu mode

INTEL_MEASURE normally measures timing of GPU events. However, it
is sometimes useful to instead measure when these gfx API calls
were requested of the driver. INTEL_MEASURE cpu can be used in
in conjunction with other driver debug capabilities, like
INTEL_DEBUG=pc for analyzing stalls/flushes or when debugger is
attached, to track which frame you're currently on or where in
the frame you're at.

Initial commit, without plumbing into anv/iris.

"INTEL_MEASURE=cpu" will collect a cpu timestamp for each
INTEL_MEASURE event instead of GPU timestamps.

Reviewed-by: Mark Janes <markjanes@swizzler.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21505>