nir: Make boolean conversions sized just like the others

Instead of a single i2b and b2i, we now have i2b32 and b2iN where N is
one if 8, 16, 32, or 64.  This leads to having a few more opcodes but
now everything is consistent and booleans aren't a weird special case
anymore.

Reviewed-by: Connor Abbott <cwabbott0@gmail.com>

src/compiler/glsl/glsl_to_nir.cpp

@@ -1527,7 +1527,7 @@ nir_visitor::visit(ir_expression *ir)
       result = supports_ints ? nir_u2f32(&b, srcs[0]) : nir_fmov(&b, srcs[0]);
       break;
    case ir_unop_b2f:
-      result = supports_ints ? nir_b2f(&b, srcs[0]) : nir_fmov(&b, srcs[0]);
+      result = supports_ints ? nir_b2f32(&b, srcs[0]) : nir_fmov(&b, srcs[0]);
       break;
    case ir_unop_f2i:
    case ir_unop_f2u: