tu: Implement fallback linear staging blit for CopyImage

tu: Implement fallback linear staging blit for CopyImage

Also, rewrite the format decision code so that we correctly decide when
the linear fallback is needed, even if UBWC is disabled. As part of
that, I also moved around some of the code to handle compressed formats
to make sure that copying compressed formats with a linear staging blit
works (this is now possible since we started allowing tiled compressed
textures).

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5007>