icons: Avoid use of rename when installing icon pack

rename does not work across filesystems. /tmp is often in
a tmpfs filesystem, and thus installing the icon pack fails.

Solve this by using a copy/delete pattern instead of rename

Fixes https://github.com/Yubico/yubioath-flutter/issues/1051

lib/oath/icon_provider/icon_pack_manager.dart

@@ -24,6 +24,7 @@ import 'package:logging/logging.dart';
 import 'package:path/path.dart';
 import 'package:path_provider/path_provider.dart';
 import 'package:yubico_authenticator/app/logging.dart';
+import 'package:io/io.dart';
 
 import 'icon_cache.dart';
 import 'icon_pack.dart';
@@ -166,7 +167,7 @@ class IconPackManager extends StateNotifier<AsyncValue<IconPack?>> {
     _iconCache.memCache.clear();
 
     // moves unpacked files to the directory final directory
-    await unpackDirectory.rename(packDirectory.path);
+    await copyPath(unpackDirectory.path, packDirectory.path);
 
     readPack();
 

pubspec.lock

@@ -357,7 +357,7 @@ packages:
     source: hosted
     version: "0.17.0"
   io:
-    dependency: transitive
+    dependency: "direct main"
     description:
       name: io
       sha256: "2ec25704aba361659e10e3e5f5d672068d332fc8ac516421d483a11e5cbd061e"

pubspec.yaml

@@ -63,6 +63,7 @@ dependencies:
   crypto: ^3.0.2
   tray_manager: ^0.2.0
   local_notifier: ^0.1.5
+  io: ^1.0.4
 
 dev_dependencies:
   integration_test: