nir/range_analysis: unsigned upper bound analysis for b2i

nir/range_analysis: unsigned upper bound analysis for b2i

fossil-db (navi21):
Totals from 93 (0.07% of 135636) affected shaders:
Instrs: 133949 -> 133899 (-0.04%); split: -0.05%, +0.01%
CodeSize: 708124 -> 707528 (-0.08%); split: -0.09%, +0.01%
Latency: 2451564 -> 2450158 (-0.06%); split: -0.06%, +0.00%
InvThroughput: 398282 -> 397345 (-0.24%)
SClause: 4441 -> 4437 (-0.09%); split: -0.18%, +0.09%
Copies: 7578 -> 7546 (-0.42%); split: -0.55%, +0.13%

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20117>