nir/range_analysis: Add "is a number" range analysis tracking

nir/range_analysis: Add "is a number" range analysis tracking

This commit is necessary to support "nir/range_analysis: Fix analysis of
fmin and fmax with NaN".

No shader-db or fossil-db changes on any Intel platform.

v2: Pack and unpack is_a_number.

v3: Don't set is_a_number of integer constants.  The bit pattern might
be NaN.

v4: Update handling of b2i32.  intBitsToFloat(int(true)) is
1.401298464324817e-45.  Return a value consistent with that.

Fixes: 405de7ccb6c ("nir/range-analysis: Rudimentary value range analysis pass")
Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/9108>