Adjust tests as affected by contracts

Contracts can affect 1) whether we get a constant and 2) which value we
are moving.

Author: tautschnig

tests/mir-opt/dataflow-const-prop/default_boxed_slice.rs

@@ -20,6 +20,6 @@ fn main() {
     // CHECK: debug a => [[a:_.*]];
     // We may check other inlined functions as well...
 
-    // CHECK: {{_.*}} = const Box::<[bool]>(
+    // CHECK: {{_.*}} = {{(const )?}}Box::<[bool]>(
     let a: A = A { foo: Box::default() };
 }

tests/mir-opt/pre-codegen/drop_boxed_slice.rs

@@ -13,6 +13,6 @@ pub unsafe fn generic_in_place<T: Copy>(ptr: *mut Box<[T]>) {
     // CHECK: [[B:_.+]] = copy [[ALIGN]] as std::ptr::Alignment (Transmute);
     // CHECK: [[C:_.+]] = move ([[B]].0: std::ptr::alignment::AlignmentEnum);
     // CHECK: [[D:_.+]] = discriminant([[C]]);
-    // CHECK: = alloc::alloc::__rust_dealloc({{.+}}, move [[SIZE]], move [[D]]) ->
+    // CHECK: = alloc::alloc::__rust_dealloc({{.+}}, move [[SIZE]], move {{.+}}) ->
     std::ptr::drop_in_place(ptr)
 }