fix: -Wunsafe-buffer-usage warning in didRegisterForRemoteNotificationsWithDeviceToken (#44348)

* chore: move as_byte_span() to new shell/common/mac_util.h

this way it can be used by multiple mm files

* fix: -Wunsafe-buffer-usage warnings in UNNotificationResponseToNSDictionary

* refactor: use base::HexEncode() instead of rolling our own

* fixup! chore: move as_byte_span() to new shell/common/mac_util.h

* fixup! chore: move as_byte_span() to new shell/common/mac_util.h

fix: move mac_util to the right place in filenames.gni

shell/common/mac_util.mm

@@ -0,0 +1,20 @@
+// Copyright (c) 2024 Microsoft, Inc.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#import <Cocoa/Cocoa.h>
+
+#include "base/containers/span.h"
+
+namespace electron::util {
+
+base::span<const uint8_t> as_byte_span(NSData* data) {
+  // SAFETY: There is no NSData API that passes the UNSAFE_BUFFER_USAGE
+  // test, so let's isolate the unsafe API use into this function. Instead of
+  // calling '[data bytes]' and '[data length]' directly, the rest of our
+  // code should prefer to use spans returned by this function.
+  return UNSAFE_BUFFERS(base::span{
+      reinterpret_cast<const uint8_t*>([data bytes]), [data length]});
+}
+
+}  // namespace electron::util