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/nir/nir_lower_bool_to_float.c

@@ -67,10 +67,6 @@ lower_alu_instr(nir_builder *b, nir_alu_instr *alu, bool has_fcsel_ne,
 
    case nir_op_b2f32: alu->op = nir_op_mov; break;
    case nir_op_b2i32: alu->op = nir_op_mov; break;
-   case nir_op_f2b1:
-      rep = nir_sne(b, nir_ssa_for_alu_src(b, alu, 0),
-                       nir_imm_float(b, 0));
-      break;
    case nir_op_b2b1: alu->op = nir_op_mov; break;
 
    case nir_op_flt: alu->op = nir_op_slt; break;