frontend/nine: Improve VS_WINDOW_SPACE_POSITION fallback

frontend/nine: Improve VS_WINDOW_SPACE_POSITION fallback

Previously we would implement position_t by
applying the inverse of the viewport, and
advertising clipping was going to occur with
the cap CLIPTLVERTS.

However when the cap is advertised, clipping
is supposed to be disabled via sw emulation
when D3DRS_CLIPPING is set to FALSE.

Since we don't support that either, instead take the
approach of disabling at least depth clipping, and
not advertising the cap.

Ideally, clipping should be totally disabled.

Acked-by: Mike Blumenkrantz <michael.blumenkrantz@gmail.com>
Signed-off-by: Axel Davy <davyaxel0@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/22644>