[code_assets] Bump ffigen to 20.0.0-dev.1 in examples

[goderbauer]

This allows us to remove the boilerplate to set up aLogger for the FfiGenerator.

Follow-up to #2694

[github-actions]

PR Health

Breaking changes ✔️

Package	Change	Current Version	New Version	Needed Version	Looking good?
code_assets	None	0.19.8	0.19.8	0.19.8	✔️
hooks	None	0.20.4	0.20.4	0.20.4	✔️
hooks_runner	None	0.23.1	0.23.1	0.23.1	✔️
objective_c	Breaking	8.1.0	9.0.0-dev.0	9.0.0	✔️

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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 symbol	Leaking sources
objective_c	_FinalizablePointer	internal.dart::_ObjCReference::new::_finalizable

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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.

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no missing headers

All source files should start with a license header.

Unrelated files missing license headers

Files
pkgs/objective_c/lib/src/ns_input_stream.dart

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[coveralls]

coverage: 82.903%. remained the same
when pulling 8fc6a26 on goderbauer:migrateexamples
into d11195c on dart-lang:main.

[dcharkes]

FFIgen and the hooks packages are not in a single pub workspace. So you'll need to publish FFIgen first. Once Dart 3.10 is out, we should be able to make it a single workspace.

Usually you get a message on your PR with a GitHub link to create a new release+tag. But I don't see any on #2694.

[dcharkes]

lgtm once green