nir: Eliminate nir_op_f2b

Builds on the work of !15121.  This gets to delete even more code
because many drivers shared a lot of code for i2b and f2b.

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

v2: Rebase on 1a35acd8d9.

v3: Update a comment in nir_opcodes_c.py. Suggested by Konstantin.

v4: Another rebase. Remove f2b stuff from Midgard.

Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20509>

src/compiler/glsl/float64.glsl

@@ -1174,12 +1174,6 @@ __int_to_fp64(int a)
    return __packFloat64(zSign, 0x412 - shiftCount, zFrac0, zFrac1);
 }
 
-bool
-__fp64_to_bool(uint64_t a)
-{
-   return !__feq64_nonnan(__fabs64(a), 0ul);
-}
-
 uint64_t
 __bool_to_fp64(bool a)
 {