panfrost: Rewrite texture descriptor creation logic

panfrost: Rewrite texture descriptor creation logic

Rather than creating partially within the Gallium create function and
monkeypatching on draw time with code split across N different files
with tight Gallium dependencies, let's streamline everything into a
series of maintainable routines in mesa/src/panfrost with no Gallium
dependencies, doing the entire texture creation in one-shot and thus
adding absolutely zero draw-time overhead (since we can allocate a BO
for the descriptor and upload ahead-of-time, so switching textures is as
cheap as switching pointers).

Was this worth it? You know, I'm not sure :|

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Tested-by: Marge Bot <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3858>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3858>