aco: add framework for testing isel and integration tests

And add some simple tests to demonstrate/test the pipeline builder and
glsl_scraper.py.

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Acked-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Acked-by: Daniel Schürmann <daniel@schuermann.dev>
Acked-by: Timur Kristóf <timur.kristof@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3521>