panvk: Preload FB attachments when required

panvk: Preload FB attachments when required

There are at least three situations where we need to preload FBs:

1. The attachment is flagged VK_ATTACHMENT_LOAD_OP_LOAD and has not been
   accessed in previous subpasses

2. The batch is implicitly split (e.g. too many jobs queued to the
   batch, wait/set events queued, ...)

3. The attachment has been written by a previous subpass

With those changes, we can get rid of panvk_emit_fb() and call
pan_emit_fbd() directly (fb_info is initialized when starting a subpass
and updated when an implicit split happens).

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Reviewed-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/12095>