Fix test union-const-eval-field for big-endian

The test fails on s390x and presumably other big-endian systems,
due to print of raw values with padding bytes.

To fix the tests remove the raw output values in the error note
with `normalize-stderr`.

Author: fneddy

tests/ui/consts/const-eval/union-const-eval-field.rs

@@ -1,5 +1,6 @@
 //@ dont-require-annotations: NOTE
 //@ normalize-stderr: "(the raw bytes of the constant) \(size: [0-9]*, align: [0-9]*\)" -> "$1 (size: $$SIZE, align: $$ALIGN)"
+//@ normalize-stderr: "([[:xdigit:]]{2}\s){4}(__\s){4}\s+│\s+([?|\.]){4}\W{4}" -> "HEX_DUMP"
 
 type Field1 = i32;
 type Field2 = f32;

tests/ui/consts/const-eval/union-const-eval-field.stderr

@@ -1,21 +1,21 @@
 error[E0080]: reading memory at ALLOC0[0x0..0x8], but memory is uninitialized at [0x4..0x8], and this operation requires initialized memory
-  --> $DIR/union-const-eval-field.rs:29:37
+  --> $DIR/union-const-eval-field.rs:30:37
    |
 LL |     const FIELD3: Field3 = unsafe { UNION.field3 };
    |                                     ^^^^^^^^^^^^ evaluation of `read_field3::FIELD3` failed here
    |
    = note: the raw bytes of the constant (size: $SIZE, align: $ALIGN) {
-               00 00 80 3f __ __ __ __                         │ ...?░░░░
+               HEX_DUMP
            }
 
 note: erroneous constant encountered
-  --> $DIR/union-const-eval-field.rs:31:5
+  --> $DIR/union-const-eval-field.rs:32:5
    |
 LL |     FIELD3
    |     ^^^^^^
 
 note: erroneous constant encountered
-  --> $DIR/union-const-eval-field.rs:31:5
+  --> $DIR/union-const-eval-field.rs:32:5
    |
 LL |     FIELD3
    |     ^^^^^^