cranelift: Remove iconst.i128 (#5075)

* cranelift: Remove iconst.i128

* bugpoint: Report Changed when only one instruction is mutated

* cranelift: Fix egraph bxor rule

* cranelift: Remove some simple_preopt opts for i128

cranelift/filetests/filetests/runtests/i128-const.clif

@@ -1,14 +0,0 @@
-test interpret
-test run
-set enable_llvm_abi_extensions=true
-target aarch64
-target s390x
-target x86_64
-target riscv64
-
-function %i128_const_0() -> i128 {
-block0:
-    v1 = iconst.i128 0
-    return v1
-}
-; run: %i128_const_0() == 0

cranelift/filetests/filetests/runtests/riscv64_issue_4996.clif

@@ -15,8 +15,10 @@ function %issue4996() -> i128, i64 system_v {
         jump block5(v13)
 
     block3:
-        v21 = iconst.i128 0
-        jump block5(v21)  ; v21 = 0
+        v20 = iconst.i64 0
+        v21 = uextend.i128 v20  ; v20 = 0
+        jump block5(v21)
+
     block5(v23: i128):
         v29 = iconst.i64 0
         return v23, v29  ; v29 = 0