ci/iris: Enable piglit gpu profile testing

This turns on pre-merge testing of piglit's GPU profile. So far the arb_sync_control tests are the only flaky ones I've found. We are also missing dmabuf import testing same as radeonsi because it apparently wasn't built in our piglit for some reason.

Note that this MR depends on !11192 (closed), and doesn't actually detect failures until #4881 (closed) is fixed.