pan/bi: Use lower_frag_coord_to_pixel_coord

pan/bi: Use lower_frag_coord_to_pixel_coord

Instead of vendoring the logic. This has a side benefit of letting NIR
optimize the generated code a bit.

total instructions in shared programs: 2687284 -> 2687281 (<.01%)
instructions in affected programs: 532 -> 529 (-0.56%)
helped: 3
HURT: 1
Inconclusive result (value mean confidence interval includes 0).

total cycles in shared programs: 140711.33 -> 140711.31 (<.01%)
cycles in affected programs: 2.53 -> 2.52 (-0.62%)
helped: 1
HURT: 0

total fma in shared programs: 22059.44 -> 22059.39 (<.01%)
fma in affected programs: 2.69 -> 2.64 (-1.74%)
helped: 3
HURT: 0

total cvt in shared programs: 14659.09 -> 14659.09 (0.00%)
cvt in affected programs: 1.56 -> 1.56 (0.00%)
helped: 1
HURT: 1

total quadwords in shared programs: 1455408 -> 1455416 (<.01%)
quadwords in affected programs: 128 -> 136 (6.25%)
helped: 0
HURT: 1

Signed-off-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23836>