st/pbo: add the image format in the download FS

st/pbo: add the image format in the download FS

In the V3D driver there is a NIR lowering step for `image_store`
intrinsic, where the image store format is required for doing the proper
lowering.

Thus, let's define it for the download FS instead of
keeping it as NONE.

v2 (Illia)
 - Use format only for drivers not supporting format-less writing.

v4 (Illia):
 - Use PIPE_CAP_IMAGE_STORE_FORMATTED to reduce combinations.

v5 (Ilia):
 - Use indirect array for download FS in not formatless-store support
   drivers.

Signed-off-by: Juan A. Suarez Romero <jasuarez@igalia.com>
Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Reviewed-by: Ilia Mirkin <imirkin@alum.mit.edu>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/13409>