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/filetests/filetests/isa/x64/sextend.clif

@@ -0,0 +1,17 @@
+test compile precise-output
+target x86_64
+
+function %f0(i8) -> i64 {
+block0(v0: i8):
+  v1 = sextend.i64 v0
+  return v1
+}
+
+;   pushq   %rbp
+;   movq    %rsp, %rbp
+; block0:
+;   movsbq  %dil, %rax
+;   movq    %rbp, %rsp
+;   popq    %rbp
+;   ret
+