cranelift: Remove booleans (#5031)

Remove the boolean types from cranelift, and the associated instructions breduce, bextend, bconst, and bint. Standardize on using 1/0 for the return value from instructions that produce scalar boolean results, and -1/0 for boolean vector elements.

Fixes #3205

Co-authored-by: Afonso Bordado <afonso360@users.noreply.github.com>
Co-authored-by: Ulrich Weigand <ulrich.weigand@de.ibm.com>
Co-authored-by: Chris Fallin <chris@cfallin.org>

cranelift/src/bugpoint.rs

@@ -762,9 +762,6 @@ fn const_for_type<'f, T: InstBuilder<'f>>(mut builder: T, ty: ir::Type) -> &'sta
     } else if ty == F64 {
         builder.f64const(0.0);
         "f64const"
-    } else if ty.is_bool() {
-        builder.bconst(ty, false);
-        "bconst"
     } else if ty.is_ref() {
         builder.null(ty);
         "null"