pan/va: Unit test va_mark_last
This pass is super easy to unit test, so we have no excuse not to test
thoroughly. va_mark_last only inserts annotations in a shader without any
annotations, so our test cases are simply annotated shaders. The CASE macro just
has to compare the case against the case with the annotations stripped and added
back with va_mark_last.
In retrospect, I should have used that technique for the flow control insertion
tests too.
Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/17091>