freedreno: Add the outline of a test for a6xx texture layout.

freedreno: Add the outline of a test for a6xx texture layout.

Trying to work out texture layout by remembering what things looked like
in texturator is hard.  Instead, let's use texture layouts from tracing
the blob as a source of truth to make sure that we pick the same layouts
they do (and don't break known-good ones).  More testcases will be added
as I fix layout bugs.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/3987>