tu: Support GMEM with layered rendering and multiview

tu: Support GMEM with layered rendering and multiview

It turns out that this actually is supported. GMEM can hold multiple
layers which are cleared, loaded, and resolved separately. The stride
between layers seems to be implicitly calculated based on the tile size,
and we have to match it when blitting to/from GMEM. One tricky thing is
that now we may realize that we don't have enough space for GMEM only
when computing the tiling config, because we may not know the number of
framebuffer layers until we have the framebuffer and too many
framebuffer layers will exhaust GMEM.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19505>