[native_assets_cli] Format with Dart 3.8

[dcharkes]

The CI will be red soon because package:native_assets_cli is opted in to a Dart 3.8 dev release.

When the CI will be red, we should land this PR to make it green again.

The PR will be red before a new dart dev release is cut. (Tuesday?)

Bug: #2194

[github-actions]

PR Health

Breaking changes ✔️

Package	Change	Current Version	New Version	Needed Version	Looking good?
native_assets_cli	Non-Breaking	0.14.0	0.15.0-0	0.14.1	✔️

API leaks ✔️

The following packages contain symbols visible in the public API, but not exported by the library. Export these symbols or remove them from your publicly visible API.

Package	Leaked API symbols

License Headers ✔️

// Copyright (c) 2025, the Dart project authors. Please see the AUTHORS file
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.

Files
no missing headers

All source files should start with a license header.

Unrelated files missing license headers

Files
pkgs/jni/lib/src/third_party/generated_bindings.dart
pkgs/objective_c/lib/src/ns_input_stream.dart

[coveralls]

coverage: 77.114%. first build
when pulling 2aa0457 on format-3-8
into a95c6c4 on main.